Wikipedia:Consensus required

The consensus required provision is a special page restriction or personal editing restriction that may be imposed by administrators as a contentious topic page restriction to limit editors from reinstating any challenged (via reversion) edits without first obtaining consensus on the talk page of the article in question.

Imposition
Administrators may impose the consensus required provision on a page or on a user, in either case pursuant to the contentious topics procedure authorised by the Arbitration Committee or pursuant to general sanctions by the Community.

Community consensus and administrators, under a contentious topics authorisation or as part of a conditional unblock, may also impose a consensus required editing restriction on an individual editor.

While it is a separate enforcement provision, a one revert per 24-hour period rule may also apply to articles and editors covered by a consensus required provision.

Process on articles
For pages or editors currently under sanctions with the "consensus required provision", editors may not reinstate any reverted edit without first obtaining consensus on the talk page.

Addition
Editor1 adds article content; Editor2 reverts, removing some or all of the added content; Prior to consensus on the article talk page, no editor may reinstate all or part of the removal.

Removal
Editor1 removes a portion of article content; Editor2 reverts, re-adding some or all of the content; Prior to consensus on the article talk page, no editor may re-remove any of the re-added content.

Process for individual editors
When an editor is placed under a consensus required editing restriction, they must demonstrate consensus for any edit they have made which is reverted whether in whole or in part on the talk page of the article(s) on which reverts took place. When imposed as an editing restriction, a sunset provision may be included. For example, the requirement to show an active recent consensus for reinstating the edit may only be active for a specified length of time after the restricted user's initial edit. Alternatively, there may be an allowance for the restricted user to reinstate the edit if there are not objections after a certain period of time rather than needing to seek an explicit prior consensus.