Territorial disputes in the South China Sea

Territorial disputes in the South China Sea involve conflicting island and maritime claims in the South China Sea by several sovereign states, namely the People's Republic of China (PRC), Taiwan (Republic of China/ROC), Brunei, Malaysia, the Philippines, Vietnam and Indonesia. The disputes involve the islands, reefs, banks, and other features of the region, including the Spratly Islands, Paracel Islands, Scarborough Shoal, and various boundaries in the Gulf of Tonkin. The waters near the Indonesian Natuna Islands, which some regard as geographically part of the South China Sea, are disputed as well.

An estimated US$3.37 trillion worth of global trade passes through the South China Sea annually, which accounts for a third of the global maritime trade. 80 percent of China's energy imports and 39.5 percent of China's total trade passes through the South China Sea. Claimant states are interested in retaining or acquiring the rights to fishing stocks, the exploration and potential exploitation of crude oil and natural gas in the seabed of various parts of the South China Sea, and the strategic control of important shipping lanes. Maritime security is also an issue, as the ongoing disputes present challenges for shipping.

A 1970s memorandum from US National Security Advisor Brent Scowcroft to then US President Ford highlighted that China, Vietnam, Taiwan, and the Philippines all claimed sovereignty over the Spratly Islands. At that time, all of these countries, except the People's Republic of China (PRC), had militarily occupied one or more of the Spratly Islands. In 2013, the PRC began island building in the Spratly Islands and the Paracel Islands region. During a US Senate hearing in May 2015, then US Assistant Secretary of Defense, David Shear reported that in the Spratly Islands, Vietnam had established 48 outposts, the Philippines had eight, China had eight, Malaysia had five, and Taiwan had one. Shear also noted that from 2009 to 2014, Vietnam was the most active claimant in terms of both upgrading outposts and reclaiming land, with approximately 60 acres reclaimed. According to Reuters, island building in the South China Sea, primarily by Vietnam and the Philippines, had been going on for decades. And Vietnam, Taiwan, and the Philippines have all deployed military forces on some of their islands, but Vietnam has not stationed any troops on its floating artificial islands. While China had been late to the island-building game, its efforts had been on an unprecedented scale; from 2014 to 2016, it had constructed more new island surface than all other nations have constructed throughout history and (unlike the other claimants) had placed military equipment, at least for a brief period, on one of its artificial islands by 2016. Also, a 2019 report from VOA that compared China and Vietnam's island building campaign in the South China Sea stated that the reason why Vietnam had been subject to little international criticism or support was because of the slower speed and widely perceived defensive nature of its island-building project.

China's actions in the South China Sea have been described as part of its "salami slicing"/"cabbage wrapping" strategies. Since 2015, the United States and other states such as France and the United Kingdom have conducted freedom of navigation operations (FONOP) in the region.

Disputes in the South China Sea region
The disputes involve both maritime boundaries and islands. There are several disputes, each of which involves a different collection of countries:
 * 1) The nine-dash line area claimed by the Republic of China (1912–1949), later the People's Republic of China (PRC), which covers most of the South China Sea and overlaps with the exclusive economic zone claims of Brunei, Indonesia, Malaysia, the Philippines, Taiwan, and Vietnam.
 * 2) Maritime boundary along the Vietnamese coast between the PRC, Taiwan, and Vietnam.
 * 3) Maritime boundary north of Borneo between the PRC, Malaysia, Brunei, Philippines, and Taiwan.
 * 4) Islands, reefs, banks and shoals in the South China Sea, including the Paracel Islands, Pratas Island, James Shoal and the Vereker Banks, Macclesfield Bank, Scarborough Shoal and the Spratly Islands between the PRC, Taiwan, and Vietnam, and parts of the area also contested by Malaysia and the Philippines.
 * 5) Maritime boundary in waters north of the Natuna Islands between the PRC, Indonesia, Taiwan and Vietnam.
 * 6) Maritime boundary off the coast of Palawan and Luzon between the PRC, the Philippines, and Taiwan.
 * 7) Maritime boundary, land territory, and the islands of Sabah, including Ambalat, between Indonesia, Malaysia, and the Philippines.
 * 8) Maritime boundary and islands in the Luzon Strait between the PRC, the Philippines, and Taiwan.

History
In 1734, the Spanish colonial government in the Philippines published the first edition of the Velarde map. According to Filipino officials and commentators, this details territories under full sovereign control of Spanish Philippines, including Scarborough Shoal (called Panacot in the indigenous language in the map) and the Spratly Islands (referred in the map as Los Bajos de Paragua), and is the earliest map to showcase the sovereignty of a nation over Scarborough Shoal and the Spratly Islands. In 1792, the Spanish colonial government of the territory of the Philippines launched the first ever survey of Scarborough Shoal on May 4, 1792. The survey, Plano de la Navigacion, was taken by Alessandro Malaspina aboard the Sta. Lucia, with Filipino comrades. The official territories of the Philippines was again published in the 1808 Carita General del Archipelago Filipino and again in the 1875 Carita General del Archipelago Filipino.

After the Spanish-American War, Spain lost and ceded the territory of the Philippines to the United States through the 1898 Treaty of Paris. The 1898 Treaty of Paris created a treaty line, where Scarborough Shoal, the Spratly Islands, and parts of Tawi-tawi continued to be under Spanish sovereignty. This led to talks between Spain and the United States, which ended upon the signing of the 1900 Treaty of Washington, which rectified retroactively the 1898 Treaty of Paris. Under the 1900 Treaty of Washington, "all islands belonging to the Philippine Archipelago, lying outside the lines described in Article III" were also ceded to the United States as part of the territory of the Philippines, where Scarborough Shoal, the Spratly Islands, and the rest of Tawi-tawi was included. From 1899 to 1902, the United States war department in the territory of the Philippines republished and reissued four times the 1875 Carita General del Archipelago Filipino with the addition of military telegraph lines, military cable lines, eastern cable company lines, and military department boundaries. The official map of the entire Philippine territory under Spanish rule was effectively adopted as the entire Philippine territory under American rule. During the 1928 Islas Palmas international case, the United States, as representative of the territory of the Philippines, reiterated in a court memorandum that the 1875 Carta General del Archipielago Filipino "is both an American official and a Spanish official map" of Philippine territory, bounding the United States on its recognition of the Scarborough Shoal and the Spratly Islands as Philippine territory. In 1930, the United States and the United Kingdom signed a treaty, where the United Kingdom recognized the territory of Philippines which included Scarborough Shoal and the Spratlys, effectively bounding the United Kingdom's successor countries as well, such as Malaysia and Brunei.

In 1932, France occupied the Paracels and laid claims on the territory. China protested and filed a Note Verbale, where it declared its claim to the Paracels for the first time in its history. Under China's international declaration, the Paracels was the "southernmost part of Chinese territory" under international law, legally binding China and negating its claim towards the Spratlys. The southernmost territory that China previously claimed was Hainan. According to the South China Sea Arbitration award, as of 1875 and until [early] 1933, no other state had claimed the Spratlys aside from the territory of the Philippines.

In July 1933, France, as a republic in itself and not as a representative of French Indochina (and its successors such as Vietnam), formally claimed six features in the Spratly Islands. China did not protest the claim of France over the Spratlys, as it never claimed the Spratly as part of its sovereign territory in the past. A few months before, France occupied some parts of the Spratlys, but not including them as part of Indochina (Vietnam). France instead claimed them as part of the Union of France. After World War II, France abandoned its claims, without any successor to its claims.



By May 1939, the Japanese occupied much of Southeast Asia, including the Paracel and Spratly Islands. During World War II, the Empire of Japan used the islands in the South China Sea for various military purposes and asserted that the islands were not claimed by anyone when the Imperial Japanese Navy took control of them. Historical accounts note that at least France had tried to occupy some of the features in the region during the 1930s, although actual sovereignty was under the American territory of the Philippines. >

According to Filipino sources, China released its "China Handbook (1937-1943)" in 1943, where it reiterated for the second time that its southernmost territory is the Paracels, specifically Triton Island. China again changed its position and published in 1947 the "1947 China Handbook", where it claimed that its southernmost territory was the Spratly Islands. This was the first time in history that China claimed the Spratlys. Under the new handbook, China also admitted on record that the Philippines and Indochina also claimed the territory, effectively making China's claim as "defective" under international law. In August 1951, Zhou Enlai, then the PRC's Foreign Minister, responding to the draft of the Treaty of San Francisco, claimed that the Paracel and Spratly Islands "have always been Chinese territory", despite Chinese historical records from its previous dynasties specifically stating that the southernmost part of China has always been Hainan. During the 1951 San Francisco Peace Conference, the USSR made a motion to grant the Paracels and the Spratlys to China, but the motion was defeated by a vote of 46 against, 3 in favour, and 1 abstention, adding the results into international historical records.

claiming the South China Sea. In 1949, the incoming government of China, which overthrew the Republic of China in the Chinese Civil War, announced that it had inherited this claim. The PRC then revised the claim to the nine-dash line by removing two of its dashes in the Gulf of Tonkin amidst warming ties with Ho Chi Minh's North Vietnam. The PRC made various claims to the islands during the 1951 treaty negotiations and the 1958 First Taiwan Strait Crisis, but none had actual sovereign effect. The PRC's 1958 declaration described China's claims in the South China Sea islands based on the nine-dotted line map. The Taiwanese (ROC) government has continued to use the eleven-dash line to this day.

Japan relinquished control of the islands in the South China Sea with the signing of the Treaty of San Francisco on 9 September 1951. The treaty, however, did not specify the new status of the islands. In the 5 September plenary session, a supplemented opinion for the People's Republic of China's sovereignty over Hoang Sa island and islands further to the South, that was rejected. Tran Van Huu as Vietnamese representative stated that “in order to annul the seeds of possible disputes, we claim our sovereignty over Hoang Sa and Truong Sa archipelagos”. However, the claims made by France over the islands before the war was claims for the Frech Republic as itself, and not as part of French Indochina (Vietnam). In 1952, the Japan-Republic of China Treaty was signed, where Japan withdrew its claims over Formosa, the Paracels, and the Spratlys but never awarded any country the sovereignty towards the Paracels and the Spratlys. The treaty positively reiterated the 1951 San Francisco Treaty, whose framers rejected China's claims over the Paracels and the Spratlys.

The Geneva Accords of 1954, which ended the First Indochina War, gave South Vietnam control of the Vietnamese territories south of the 17th Parallel. The South Vietnamese government claimed the Paracels in the Spratly despite no actual sovereignty on the Spratlys. In 1955, France clarified through international notes that the Spratlys belonged to "the French Union, not Vietnam", a few years when it stated in 1949 through official international documents that the French claim was specifically "not attached to Vietnam" when the "former colony of Conchinchina was ceded to the Associated State", effectively blocking any claim of Vietnam towards the Spratlys.

In 1974, when a North Vietnamese victory in the Vietnam War began to seem probable, the PRC used military force in the Paracel Islands and took Yagong Island and the Crescent group of reefs from South Vietnam. The government of the PRC wanted to prevent the Paracel islands from falling under the control of North Vietnam, which at the time was an ally of the Soviet Union. After not resisting during the initial Vietnamese attack, the PRC launched what they regarded as a "counterattack in self-defense". The United States, in the middle of détente with the PRC, gave a non-involvement promise to the PRC, which enabled the People's Liberation Army Navy to take control of the South Vietnamese islands.

In the later half of 1970s, the Philippines and Malaysia began referring to the Spratly Islands as being included in their own territory. On 11 June 1978, the Philippines through Presidential Decree No. 1596, declared the north-western part of the Spratly Islands (referred to therein as the Kalayaan Island Group) as Philippine territory.

In 1988, the PRC and Vietnam fought each other near the Johnson Reef. The PRC had obtained a permit from the Intergovernmental Oceanographic Commission to build five observation posts for the conduction of ocean surveys, and one of the permitted observation posts was allowed to be located in the Spratly islands region. The PRC chose to build its observation post on the Fiery Cross Reef, which was isolated from the other islands in the region and was not occupied by any state at the time. When it started to build the observation post in the terra nullius Fiery Cross Reef, Vietnam sent its navy to the area to monitor the situation. The two states clashed near the Johnson Reef, and after the clash, China occupied the Johnson Reef.

In 1990, 1994, and 1997, the People's Republic of China released its "An Atlas of Ancient Maps of China" in three volumes, wherein in all maps presented in its official documents, the southernmost territory of China was the island of Hainan. No ancient map showed Chinese sovereignty over any territory south of Hainan.

In 1994, the PRC occupied Mischief Reef, located some 250 miles from the Philippine coast. Occupation was made in the middle of an energy resources race in the Spratlys, where China lacked a presence, while the other countries were starting their oil exploration businesses. Mischief Reef marked the first time the PRC had a military confrontation with the Philippines, an ally of the United States.

The occupation and/or control of most parts of the Spratly and Paracel islands did not change significantly from the 90s to the 2000s. To this day, the PRC controls all of the islanda in the Paracels. In the Spratlys, Vietnam controls the most islands with 29 in total, while the Philippines has control of eight islands, Malaysia with 5, the PRC with 5, and the ROC with 1.

However, in 2011, tensions started to increase again in the territory. In February, the Chinese frigate Donguan fired three shots at Philippine fishing boats near Jackson atoll. In May, the Vietnamese Binh Minh 02 oil and gas survey ship clashed with three Chinese maritime patrol vessels some 600 km south of China's Hainan island.

Beginning in 2012, the islands became more increasingly militarized. The ROC started the construction of an antenna tower and runway on the Taiping island in February, allowing the island to accommodate various military aircraft. On the Vietnam occupied Sand Cay and West Reef islands, upgrades and land reclamation projects were also started at this time.

In April 2012, the PRC unilaterally invaded the Philippine-controlled Scarborough Shoal, forcing the Philippines to file the Philippines vs China international case under the rules of UNCLOS. In 2016, the Philippines won the case, and the international court effectively invalidated the dash line invented by China to claim an entire sea. During the court proceedings, China itself filed an official and binding international "Position Paper", where it recognized the 1900 Treaty of Washington. Under the said treaty, Scarborough Shoal and the Spratlys was recognized as part of the territory of the Philippines. China also reiterated that it recognizes the treaty between the United States and the United Kingdom, where both nations reiterated the recognition of Philippine territory, which included Scarborough Shoal and the Spratlys. The move came as a surprise to the Filipino delegation, where Associate Justice Antonio Carpio stated that China likely did not read the full text of the treaties they reiterated.

In September 2018, a South Korean navy destroyer traveled into what China saw as its territorial waters. A South Korean government official said the navy destroyer was taking refuge from a typhoon and not challenging maritime claims, but he declined to comment on whether Seoul believed the disputed waters belonged to China. A Chinese Defense Ministry spokesman said the ship broke Chinese law by entering its 12-nautical-mile-wide territorial sea around the Paracel Islands without seeking prior permission, but said Beijing accepted South Korea's explanation.

On 22 December 2020, the PRC claimed that the guided missile destroyer John S McCain had been "expelled" after it “trespassed” into Chinese territorial waters close to the Spratly Islands. However this claim has been disputed by the US Navy.

In March 2021, 220 Chinese fishing boats were seen moored around Whitsun Reef in the Spratly Islands, a reef claimed by the Philippines as part of its exclusive economic zone. Philippines Defense Secretary Delfin Lorenzana accused China of "provocative action of militarizing the area".

On June 17, 2024, China and the Philippines traded accusations over a collision in the South China Sea, with Manila saying its armed forces would resist Beijing's actions in the disputed waters, the latest in an increasingly testy series of confrontations. The U.S. State Department condemned what it called "escalatory and irresponsible" actions by China and reaffirmed that its mutual defense treaty with the Philippines applied to any armed attacks on Philippine armed forces, vessels, or aircraft anywhere in the South China Sea.

"China's dangerous and reckless behavior in the West Philippine Sea shall be resisted by the Armed Forces of the Philippines," Gilberto Teodoro, Manila's defense secretary, said in a statement. "China's actions are the true obstacles to peace and stability in the South China Sea."

2011 agreement
On 20 July 2011, the PRC, Brunei, Malaysia, the Philippines, Taiwan and Vietnam agreed a set of preliminary guidelines on the implementation of the DOC (Declaration of Conduct of Parties in the South China Sea) which would help resolve disputes. This set of guidelines is based on an earlier agreement, also called DOC, from 2002, between China and the ASEAN Member States.

The agreement was described by the PRC's assistant foreign minister, Liu Zhenmin, as "an important milestone document for cooperation among China and ASEAN countries". Some of the early drafts acknowledged aspects such as "marine environmental protection, scientific research, safety of navigation and communication, search and rescue and combating transnational crime", although the issue of oil and natural gas drilling remains unresolved. "Following the spirit of the Declaration on the Conduct of Parties in the South China Sea (DOC), China and ASEAN countries actively advanced the consultations on the Code of Conduct (COC) in the South China Sea," with the forecast that the COC will be completed by 2021.

Chinese objection to Indian military presence and oil exploration
On 22 July 2011, the INS Airavat, an Indian amphibious assault vessel on a friendly visit to Vietnam, was reportedly contacted 45 nautical miles from the Vietnamese coast in the disputed South China Sea by a party identifying itself as the PLA Navy and stating that the ship was entering PRC waters. A spokesperson for the Indian Navy explained that as no ship or aircraft was visible, the INS Airavat proceeded on her onward journey as scheduled. The Indian Navy further clarified that "[t]here was no confrontation involving the INS Airavat. India supports freedom of navigation in international waters, including in the South China Sea, and the right of passage in accordance with accepted principles of international law. These principles should be respected by all."

In September 2011, shortly after the PRC and Vietnam signed an agreement seeking to contain a dispute over the South China Sea, India's state-run explorer, Oil and Natural Gas Corporation (ONGC) said that its overseas investment arm, ONGC Videsh Limited, had signed a three-year agreement with PetroVietnam for developing long-term co-operation in the oil sector, and that it had accepted Vietnam's offer of exploration in certain specified blocks in the South China Sea. However, this agreement between India and Vietnam has provoked attacks from the PRC In response, PRC Foreign Ministry spokesperson Jiang Yu, without referring to India by name, stated:"'As for oil and gas exploration activities, our consistent position is that we are opposed to any country engaging in oil and gas exploration and development activities in waters under China's jurisdiction. We hope the foreign countries do not get involved in South China Sea dispute.'" An Indian foreign ministry spokesman responded, "The Chinese had concerns, but we are going by what the Vietnamese authorities have told us and we have conveyed this to the Chinese." The Indo-Vietnamese deal was also denounced by the Chinese state-run newspaper Global Times.

Chinese policy on the South China Sea
In spring 2010, PRC officials reportedly communicated to US officials that the South China Sea was "an area of 'core interest' that is as non-negotiable" and on par with Taiwan and Tibet on the national agenda. However, Beijing appeared to have backed away from that assertion in 2011.

In October 2011, the Chinese Communist Party-owned Global Times tabloid editorialised on the South China Sea territorial disputes under the banner "Don't take peaceful approach for granted". The article referenced incidents earlier that year involving the Philippines and South Korea detaining PRC fishing boats in the region. "If these countries don't want to change their ways with China, they will need to prepare for the sounds of cannons. We need to be ready for that, as it may be the only way for the disputes in the sea to be resolved." Responding to questions about whether this reflected official policy, a Chinese Foreign Ministry spokeswoman stated the country's commitment "to resolving the maritime dispute through peaceful means."

In July 2014, Professor Alan Dupont of the University of New South Wales was reported as saying that the Chinese government appeared to be directing its fishing fleet into disputed waters as a matter of policy.

From 2013 to the beginning of 2018, China carried out land reclamation in the South China Sea. The construction of the islands has been completed. The three island airports of Meiji Reef, Zhubi Reef, and Yongshu Reef have been completed.

In August 2019, China's paramount leader Xi Jinping told Philippine President Rodrigo Duterte that China would not recognise or abide by the arbitration decision. China rejects the arbitration proceedings as illegitimate because China excluded itself from compulsory arbitration in its ratification of the 2006 United Nations Convention on the Laws of the Seas (UNCLOS). Xi made his comments during a visit by Duterte to Beijing, with discussions between the two leaders. This stance by Beijing is in line with the July 2019 publishing of a Chinese White Paper, "China's National Defense in the New Era," which details China's armed strength and repeatedly mentions deployment in the South China Sea. On 22 September 2020, in a recorded speech at the opening of the 75th session of the UN General Assembly, the Philippine President, Rodrigo Duterte reaffirmed the Hague ruling rejecting most of China's claims to disputed waters, and said "The award is now part of international law, beyond compromise and beyond the reach of passing governments to dilute, diminish, or abandon."

Oil and gas development
The area is said to be rich in oil and natural gas deposits; however, the estimates are highly varied. The Chinese Ministry of Geological Resources and Mining estimated that the South China Sea may contain 17.7 billion barrels of crude oil, compared to the oil rich country of Kuwait which has 13 billion barrels. In the years following the announcement by the PRC ministry, the claims regarding the South China Sea islands intensified. However, other sources claim that the proven reserves of oil in the South China Sea may only be 7.5 billion barrels, or about 1.1 billion barrels. According to the US Energy Information Administration (EIA)'s profile of the South China Sea region, a US Geological Survey estimate puts the region's discovered and undiscovered oil reserves at 11 billion barrels, as opposed to a PRC figure of 125 billion barrels. The same EIA report also points to the wide variety of natural gas resource estimations, ranging from 190 trillion cubic feet to 500 trillion cubic feet, likely located in the contested Reed Bank".

Competing claims in the oil and gas-rich South China Sea have stifled the development and exploitation of these resources. To break from this, the Philippines and China agreed to a Memorandum of Understanding (MoU) on Cooperation on Oil and Gas Development in November 2018, where joint-use of, and not ownership over assets underlies the agreement. In the past, Chinese naval patrols deterred Filipino PXP Energy from exploring gas deposits in disputed waters, like the Reed Bank, such that this type of agreement may allow for the claimant states to jointly develop the natural gas in the offshore area. The mechanism of joint agreements is not new, with Malaysia and Vietnam having forged a similar mechanism in 1992, while Malaysia and Thailand reached understandings in 1979 and 1990 over the development of gas-rich disputed waters.

Philippines
The Philippines began exploring the areas west of Palawan for oil in 1970. Exploration in the area began in Reed Bank/Tablemount. In 1976, gas was discovered following the drilling of a well. However, the PRC's complaints halted the exploration. On 27 March 1984, the first Philippine oil company discovered an oil field off Palawan, which is an island province bordering the South China Sea and the Sulu Sea. These oil fields supply 15% of annual oil consumption in the Philippines.

Vietnam
Vietnam and Japan reached an agreement early in 1978 on the development of oil in the South China Sea. By 2012 Vietnam had concluded some 60 oil and gas exploration and production contracts with various foreign companies. In 1986, the "White Tiger" oil field in the South China Sea came into operation, producing over 2,000 tons of crude oil per year, followed by "The Bear" and "Dragon" oil fields. The country is a net importer of oil products. In 2009 petroleum accounted for 14 percent of Vietnamese government income, down from 24 percent in 2004.

In 2017, after Chinese pressure, the Vietnamese government ordered Spain's Repsol to stop drilling in the disputed area. A joint-venture of Japanese Inpex and Petrovietnam planned to start drilling in the disputed area in 2021.

China
China's first independently designed and constructed oil drilling platform in the South China Sea is the Ocean Oil 981 (海洋石油981). The major shareholders are JPMorgan Chase (19%), Commonwealth Bank (14%), T Rowe Price (6%), and BlackRock (5%). It began operation on 9 May 2012 in the South China Sea, 320 km southeast of Hong Kong, at a depth of 1,500 m and employing 160 people. On 2 May 2014 the platform was moved near to the Paracel Islands, a move Vietnam stated violated their territorial claims. Chinese officials said it was legal, stating the area lies in waters surrounding the Paracel Islands which China occupies and militarily controls.

Incidents involving fishermen
Prior to the territorial disputes, fishermen from involved countries tended to enter each other's controlled islands and Exclusive Economic Zones (EEZ) leading to conflicts with the authorities that controlled the areas as they were unaware of the exact borders. As well, due to depletion of the fishing resources in their maritime areas, they were forced to fish in the neighbouring countries' areas.

In 2006 the captain of a Taiwanese fishing boat was shot dead and a crewman wounded when their boat was reportedly attacked by pirates wearing military uniforms. Philippine authorities assured the Taiwan Ministry of Foreign Affairs that no Filipino naval or coast guard personnel were involved in the incident. The incident occurred in the Bashi Channel which is adjacent to the South China Sea.

In May 2013 a Taiwanese fisherman on Guang Da Xing No. 28 operating 43 nautical miles east of Balintang Island on the eastern side of the Balintang Channel was killed by machine gun fire from a Philippine Coast Guard vessel. In September 2019, seven members of the coast guard and a police man involved were convicted and sentenced to imprisonment and civil damages.

In the spring of 2014, China and Vietnam clashed again over China's Haiyang Shiyou oil rig in Vietnam's EEZ. The incident left seventeen Vietnamese injured and damaged ships of both countries.

Although Indonesia is not part of claims in the South China Sea dispute, after Joko Widodo became President of the country in 2014, he instituted a policy in 2015 that, if any foreign fishermen were caught illegally fishing in Indonesian waters, their vessels would be destroyed. The president wanted to make maritime resources, especially fisheries, a key component of his administration's economic policy. Since the policy's initiation, fishing vessels drawing from many neighbouring countries were destroyed by Indonesian authorities. On 21 May 2015, around 41 fishing vessels from China, Vietnam, Thailand and the Philippines were destroyed. On 19 March 2016, the China Coast Guard prevented the detention of Chinese fishermen by Indonesian authorities after Chinese fishermen were caught fishing near the waters around Natuna, leading to a protest by Indonesian authorities; the Chinese ambassador was subsequently summonsed as China had considered the areas to be "Chinese traditional fishing grounds". Further Indonesian campaigns against foreign fishermen resulted in the destruction of 23 fishing boats from Malaysia and Vietnam on 5 April 2016.

Out of the 556 ships Indonesia had destroyed from October 2014 to 2019 for violating rules, 312 of them were from Vietnam, 91 were from the Philippines, 87 were from Malaysia, 26 were local, and 3 were from China. According to a 2023 Tempo report, Thai vessels also often illegally fished in Indonesian waters. The areas in the South China Sea had also become known for Indonesian pirates, with frequent attacks on Malaysian, Singaporean and Vietnamese vessels as well as leading to hijacking such as the MT Orkim Harmony and MT Zafirah hijacking incidents. The continuing war against foreign fishermen by Indonesia led to protests by Vietnam in late 2016, when a Vietnamese fisherman was killed after being shot by Indonesian authorities. Attacks have also come from Filipino and Moro pirates arriving from the Sulu Sea; a Vietnamese fisherman was killed by Filipino pirates in late 2015.

In 2017, two Vietnamese fishermen died from gunshot wounds from a pursuing Philippine Navy patrol boat about 40 miles off the city of Bolinao, Pangasinan. A police report said that the boats had collided after the navy had fired warning shots; the Philippine government said that it had promised Vietnam a “fair and thorough” investigation.

On 8 May 2019, Vietnam's ambassador to Malaysia was summoned to the Malaysian Ministry of Foreign Affairs to explain on the high number of encroachments by Vietnamese vessels into the country's waters. Three months later, Mahathir Mohamad who was Prime Minister at the time also raised the issue with his Vietnamese counterpart. According to the Malaysia Maritime Enforcement Agency, most illegal fishing incidents in Malaysian waters have come from Vietnamese vessels, followed by Thai ones.

Teodoro Locsin Jr., the Filipino Secretary of Foreign Affairs, said in 2020 that the Philippines was building a maritime fleet that could swarm areas in the South China Sea. He said the fleet build up was because of China which was also doing the same thing. He also said if one of the vessels got hit, the Filipino defense treaty with the United States would also be activated.

As part of a group of cooperation agreements announced in December 2023, the China and Vietnam announced joint patrols in the Gulf of Tonkin and a hotline to handle South China Sea fishing incidents.

International Law
The doctrine of intertemporal law was established after the Island of Palmas Case ruling. Under the doctrine, treaty rights are assessed under the laws in force at the time the treaty is made, not at the time a dispute takes place.

In the Eastern Greenland Case between Norway and Denmark, the critical date doctrine was established in 1933. It was ruled by the Permanent Court of International Justice (PCIJ) that the Norwegian proclamation on July 10, 1931, annexing Eastern Greenland was the "critical date" in that specific case.

Under the principle of Uti possidetis juris, the boundaries of former colonies must be respected by all states. It was established after the 1986 Frontier Dispute case between Burkina Faso and Mali). The ICJ ruled that uti possidetis juris is a "general principle, which is logically connected with the phenomenon of the obtaining of independence, wherever it occurs. It's obvious purpose is to prevent the independence and stability of new States being endangered by fratricidal struggles provoked by the challenging of frontiers following the withdrawal of the administering power…Its purpose, at the time of the achievement of independence by the former Spanish colonies of America, was to scotch any designs which non-American colonizing powers might have on regions which had been assigned by the former metropolitan State to one division or another, but which were still uninhabited or unexplored."

Maps cannot establish title to territory unless if it is attached to a treaty. Moreover, maps unilaterally produced by a state, even if not attacked to a treaty, can bind the producing state if it is "adverse to its interest". This was established in the 2002 Delimitation of the Border between the State of Eritrea and Ethiopia case, and was affirmed further in the Pedra Blanca arbitration between Malaysia and Singapore in 2008, when the ICJ ruled: "The map still stands as a statement of geographical fact, especially when the State adversely affected has itself produced and disseminated it, even against its own interest."

The dash-line used by China to assign to itself almost the entire South China Sea is invalid as per the 2016 South China Sea Arbitration case ruling.

Security summits
The Shangri-La Dialogue serves as the "Track One" exchange forum on security issues surrounding the Asia-Pacific region. The South China Sea territorial disputes has dominated proceedings at the conference in recent years. The Council for Security Cooperation in the Asia Pacific is the "Track Two" forum for dialogue on security issues.

In February 2016, U.S. President Barack Obama initiated the US-ASEAN Summit at Sunnylands in Rancho Mirage, California for closer engagement with the Association of Southeast Asian Nations. Territorial disputes in the South China Sea were a major topic, but its joint statement, the "Sunnylands Declaration", did not name the South China Sea, instead calling for "respect of each nation's sovereignty and for international law". Analysts believe it indicates divisions within the group on how to respond to China's maritime strategy.

Analysis
According to Mohan Malik, a professor at the Asia-Pacific Center for Security Studies of the United States Department of Defense, the vast majority of international legal experts have concluded that China's claim to historical title, meaning full sovereign authority, is invalid. U.S. Naval War College professor Peter A. Dutton writes that the Chinese government sees itself as fundamentally above the law and beyond accountability to others, especially smaller states.

According to Bill Hayton, an analyst at Chatham House, no claimant undertook any physical act of sovereignty on any of the disputed islands before the 19th century.

According to Johns Hopkins University professor and Carnegie Endowment for International Peace analyst Isaac B. Kardon, Chinese maritime rules mostly mirror the international law except for certain crucial areas reflecting its political interests.

UNCLOS tribunal
In July 2016, the Permanent Court of Arbitration (PCA), an internationally agreed arbitration tribunal sitting in the Hague and constituted under Annex VII of the United Nations Convention on the Law of the Sea (UNCLOS), ruled comprehensively against the People's Republic of China's South China Sea maritime claims in the arbitration. This tribunal did not rule on the ownership of the islands or delimit maritime boundaries.

However, both mainland China and Taiwan stated that they did not recognize the tribunal and insisted that the matter should be resolved through bilateral negotiations with other claimants. On 17 September 2020, France, Germany, and the United Kingdom issued a joint note verbale recognizing the PCA ruling and challenging China's claims.

In response to the ruling, Graham Allison stated, "None of the five permanent members of the UN Security Council have ever accepted any international court's ruling when (in their view) it infringed their sovereignty or national security interests. Thus, when China rejects the Court's decision in this case, it will be doing just what the other great powers have repeatedly done for decades."

Australia
On 25 July 2020 Australia rejected China's claims to the South China Sea and filed a statement with the United Nations that said: "Australia rejects any claims to internal waters, territorial sea, exclusive economic zone and continental shelf based on such baselines," and there is "no legal basis" to draw the nine-dash line around the Four Sha archipelagos, Paracel and Spratly Islands or low-tide maritime zones. They encourage the claimants to resolve their disputes peacefully.

Cambodia
Cambodia has backed China over the dispute in ASEAN meetings, preventing consensus over unified ASEAN action. Anti-Vietnamese sentiment due to Vietnam's conquest of previously Cambodian lands, giving the Vietnamese a privileged status and encouragement of Vietnamese settlers in Cambodia during French colonial rule, and the occupation of Cambodia after the ousting of the Khmer Rouge has led to anti-Vietnamese feelings against ethnic Vietnamese in Cambodia and against Vietnam, and in turn has led to pro-China sentiment among the Cambodian government and the Cambodian opposition, including in the South China Sea.

India
India says that the South China Sea was "part of global commons and India has an abiding interest in peace and stability in the region... We firmly stand for the freedom of navigation and overflight and unimpeded lawful commerce in these international waterways, in accordance with international law, notably UNCLOS." This was seen as largely backing the US position.

Indonesia
Since early in the South China Sea dispute, Indonesia has repeatedly asserted its position as a non-claimant state in the South China Sea dispute, and often positioned itself as an "honest broker". However, parts of China's unilaterally claimed nine-dash line overlap Indonesia's exclusive economic zone near the Natuna islands. Although China has acknowledged Indonesia's sovereignty over the Natuna islands, the PRC has argued that the waters around the Natuna islands are Chinese "traditional fishing grounds". Indonesia quickly dismissed China's claim, asserting that China's nine-dash line claim over parts of the Natuna islands has no legal basis. In November 2015, Indonesia's security chief Luhut Pandjaitan said Indonesia could take China before an international court. Indonesia filed a comment with the Permanent Court of Arbitration regarding China's claim in the arbitration.

Chinese fishing vessels – often escorted by Chinese coastguard ships – have repeatedly been reported to have breached Indonesian waters near the Natuna islands. On 19 March 2016, for example, Indonesian authorities tried to capture a Chinese trawler accused of illegal fishing in Indonesian waters, and arrested the Chinese crew. They were prevented from towing the boat to harbour by a Chinese coast guard vessel which reportedly "rammed" the trawler in Indonesian waters. "To prevent anything else occurring, the Indonesian authorities let go of the Chinese boat and then left toward Natuna, still with eight fishermen and the captain on board," said Arrmanatha Nasir, a spokesman for Indonesia's Foreign Ministry. Indonesia still has the Chinese crew in custody. On 21 March 2016, minister for fisheries and maritime affairs Susi Pudjiastuti summoned the Chinese ambassador, Xie Feng, and discussed this matter. Indonesia insists that they have the right to prosecute the Chinese trawler crew, despite Beijing's demand to release their eight fishermen. Arif Havas Oegroseno, the government official of maritime security, said that the Chinese claim of "traditional fishing grounds" was not recognised under the 1982 United Nations Convention on the Law of the Sea. This incident prompted security minister Luhut Pandjaitan to deploy more troops and patrol boats, and to strengthen the Ranai naval base in the area.

Following the clashes, on 23 June 2016, Indonesian President Joko Widodo visited the Natuna islands on a warship to demonstrate Indonesia's authority. He led a high-level delegation, which included the Commander of the Indonesian National Armed Forces (TNI) and state ministers. Security Minister Luhut Pandjaitan said it was meant to send a "clear message" that Indonesia was "very serious in its effort to protect its sovereignty".

Following the Permanent Court of Arbitration decision on 12 July 2016, Indonesia called on all parties involved in the territorial dispute to exercise self-restraint and to respect applicable international laws.

Indonesia challenged the Chinese nine-dash historical claim by arguing that if the historical claims can be used on presenting the territorial naval claims, Indonesia might also use its historical claims on the South China Sea by referring to the ancient influence of the Srivijaya and Majapahit empires.

Indonesia's EEZ extends 200 nautical miles (370 km) from its shores, which around Natuna means it is slightly intersected by China's nine-dash line, defining its widely disputed claim to most of the South China Sea. In 2014–2015, the presence of the TNI on the islands was reinforced, which the Indonesian government hoped would reduce the chance of any conflict. Then in early 2020, a further 600 troops were deployed and eight navy warships from the Indonesian Navy including Ahmad Yani-class frigates, Bung Tomo-class corvettes, and Kapitan Pattimura-class ASW corvettes were sent to the area with support from the Indonesian Navy Naval Aviation CN-235 MPA, the Indonesian Air Force also sent 4 F-16 and a Boeing 737-2x9 Surveillance, and put BAE Hawk aircraft nearby on alert after Chinese fishing vessels increased illegal activity within the EEZ, escorted by a Chinese Coast Guard vessel. A recent visit to the area by President Joko Widodo displayed Indonesia's resolve to not overlook such incursions.

Japan
Japan has used "normative power" via strategic foreign aid to certain claimants in the dispute such as the Philippines and Vietnam in order to assert its presence in the region as promoting the "rule of law at sea."

Singapore
Singapore has reiterated that it is not a claimant state in the South China Sea dispute and has offered to play a neutral role in being a constructive conduit for dialogue among the claimant states. Prime Minister Lee Hsien Loong said during his official visit to the US that he hoped all countries will respect international law and the outcome of arbitration. The spokesperson of China Hua Chunying responded in a press conference said that the award by the Arbitral Tribunal was "illegal" and "invalid", and thus not binding at all. She urged Singapore to respect China's position, stay objective and impartial.

Sri Lanka
Kabir Hashim, General Secretary of the United National Party, has said that the South China Sea disputes should be resolved through bilateral talks between China and the countries concerned rather than being subject to external forces.

Thailand
Thailand as one of the member of ASEAN played a coordinating role in facilitating China and ASEAN members involved in the dispute in hope of reaching peaceful resolution. Despite its domestic political turmoil, the Thai government relied on its Ministry of Foreign Affairs' expertise on international dispute. It took the initiative to hold several meetings with parties concerned. Thailand's first attempt was hosting the ASEAN–China Senior Officials' Meeting Retreat in Pattaya, Thailand 2012. Via this meeting, Wang Yi, the Chinese Foreign Minister called for a joint development of resources in South China Sea. Bangkok was viewed as a South China Sea neutral player because it is not a claimant and did not have disputes in the South China Sea with China. After several meetings, the 6th ASEAN–China SOM on DOC was the first official consultation on the Code of Conduct (COC) was formed with all parties agreement to push forward the drafting of COC. Thai-China relationship was generally seen as positive. Thailand's neutral position enabled it to act as a mediator and influence discussions among parties involved.

United States
In 1974, the PRC received a non-involvement promise from the United States when it occupied the Yagong Island and the Crescent Group from South Vietnam. The United States officially addressed the South China Sea dispute for the first time in 1995, when its statement focused on the peaceful resolution of disputes, peace and stability, freedom of navigation, neutrality over the question of sovereignty, and respect of maritime norms. The 1995 statement did not name any states by their names.

The 1995 policy was changed in 2010, when the administration of the President Obama felt that even though the United States cannot take sides in the dispute, it still has to make a statement that it is not passively accepting the assertive actions taken in the region. At the July 2010 Association of Southeast Asian Nations Regional Forum meeting in Hanoi, Secretary of State Hillary Clinton gave a speech on resolving the disputes in the region without coercion and unequivocally stating that the South China Sea was a matter of U.S. national interest. Her comments were countered by China's Foreign Minister Yang Jiechi as "in effect an attack on China," and he warned the United States against making the South China Sea an international issue or multilateral issue.

In 2012, a United States State Department press statement identified the PRC as an assertive state in the region and communicated United States concerns about the developments in the area. Also in 2012, Secretary Clinton testified in support of congressional approval of the Law of the Sea Convention, which would strengthen U.S. ability to support countries that oppose Chinese claims to certain islands in the area. On 29 May 2012, a spokesman for the Chinese Foreign Ministry expressed concern over this development, stating that "non-claimant Association of South East Asian Nations countries and countries outside the region have adopted a position of not getting involved into territorial disputes." In July 2012, the United States Senate passed resolution 524, initially sponsored by Senator John Kerry, stating (among other things) the United States' strong support for the 2002 declaration of conduct of parties in the South China Sea, reaffirms the United States' commitment to assist the nations of Southeast Asia to remain strong and independent, and supports enhanced operations by the United States armed forces in the Western Pacific.

In 2014, the United States responded to China's claims over the fishing grounds of other nations by saying that "China has not offered any explanation or basis under international law for these extensive maritime claims." USN CNO Jonathan Greenert then pledged American support to the Philippines in its territorial conflicts with the PRC. The Chinese Foreign Ministry asked the United States to maintain a neutral position on the issue. In 2014 and 2015, the United States continued freedom of navigation operations ("FONOPs"), including in the South China Sea.

In May 2015, the Wall Street Journal reported that the “US Navy regularly conducts freedom of navigation transits in the region ... [but] has yet to receive explicit authorization from the administration to do so within 12 nautical miles of the artificial islands”. At the Shangri-La Dialogue on May 30, 2015, Secretary of Defense Ash Carter drew attention to China's artificial islands, stating that: “China is out of step with...international rules [as] turning an underwater rock into an airfield simply does not afford the rights of sovereignty or permit restrictions on international air or maritime transit. . . . All countries should have the right to freedom of navigation [and] America, alongside its allies and partners in the [region] will not be deterred from exercising these rights.” On September 18, 2015, the Chinese Foreign Ministry replied by stating that “China, like the US, champions navigation freedom in the South China Sea, but opposes any country’s attempt to challenge China’s territorial sovereignty ... under the pretext of safeguarding navigation freedom.” At the start of October 2015, the US Department of Defense made it clear that a FONOP within 12 nautical miles of one of China's artificial islands was “not a question of if, but when”, and by mid-October 2015, US officials said the FONOP was expected "within days". On 27 October 2015, the US destroyer USS Lassen navigated within 12 nautical miles of reclaimed land in the Subi Reef as the first in a series of "Freedom of Navigation Operations". This was the first time since 2012 that the US has directly challenged China's claims of the island's territorial limit. On 8–9 November 2015, two US B-52 strategic bombers flew near artificial Chinese-built islands in the area of the Spratly Islands and were contacted by Chinese ground controllers but continued their mission undeterred.

President Trump's administration increased the frequency of freedom of navigation operations in the South China Sea. In June 2020, US Ambassador to the United Nations Kelly Craft sent a letter to the U.N. secretary general explaining the US position on China's "excessive maritime claims." On 14 July 2020, US Secretary of State Mike Pompeo declared China's claims and coercions of in parts of the South China Sea “completely unlawful”. On 26 August 2020, the US sanctioned individuals and 24 Chinese companies linked to construction and militarization of the artificial islands.

Publications by US think tanks have made recommendations for courses of actions that the United States could take in response to PRC activities in the South China Sea.

The US Navy has conducted freedom of navigation drills in the South China Sea to counter Vietnamese claims in the region, particularly around the Côn Đảo islands.

The US, Japan and the Philippines conducted military exercises intended to "(ensure) that all countries are free to fly, sail, and operate wherever international law allows" on April 7, 2024, in advance of a planned trilateral summit. The Southern Theater Command of China's PLA issued statements saying it was organizing "joint naval and air combat patrols in the South China Sea" and "All military activities that mess up the situation in the South China Sea and create hotspots are under control".

Disputes vs. UNCLOS
One observer, a visiting assistant professor of international law at De La Salle University, Philippines, remarked: "While the PRC, ROC and Vietnam claim the entire Spratly archipelago because of what they perceive to be their 'historical right' to the area, Brunei, Malaysia, and the Philippines base their respective claims on the stipulations regarding continental shelves outlined in UNCLOS. [...] While some would argue that the historical claims of the PRC, ROC, and Vietnam should be discarded because they do not conform to the stipulations of UNCLOS, this is unrealistic. The notion of historical entitlement sits at the foundation of their claims to the Spratly archipelago and are unlikely to dissipate simply because analysts choose to ignore them. As a result, any proposed framework must address such concerns."

That observer concludes, "UNCLOS must be applied to the Spratly question in a way that accounts for the unique characteristics of the dispute."