Sibbach v. Wilson & Co.

Sibbach v. Wilson & Co., 312 U.S. 1 (1941), was a decision by the United States Supreme Court in which the Court held that under American law important and substantial procedures are not substantive, rather they are still considered procedural, and federal law applies.

This was a post-Erie decision, and thus the decision whether to apply the law of the state of jurisdiction or uniform federal rules depended on whether the rule in question was procedural or substantive in nature.