Also known as: substantive and procedural · substance vs procedure · substance versus procedure · substantive law · procedural law
Written by attorneys · grounded in primary & secondary sources — see below
A distinction between rules that determine the rights and duties of parties and rules that govern the manner in which those rights are enforced in court. In diversity cases a federal court applies state rules falling on the substantive side of the line and federal rules falling on the procedural side.
Simon Stern, a citizen of State A, sued Solstice Ventures, a State B corporation, in federal court in State B for breach of a supply contract formed in State B. The court applied State B contract law and its choice-of-law rules to decide which state's substantive rules governed the claim. The outcome turned on whether the federal court would create its own general common law or follow the state substantive rules.
Sophia Singh prevailed on a state-law claim in federal court and filed a motion under Rule 54 for attorney fees. Because the underlying substantive law treated fees as an element of damages rather than a post-judgment cost, the court required proof at trial instead of a separate motion. The timing and method of recovery therefore followed the substantive characterization.
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Samuel Soto, a State A citizen, sued Sentinel Security, a State C corporation, in federal court in State B after an accident in State A. The court applied State B choice-of-law rules to decide whether State A or State B tort law governed the claim. The selection of the governing substantive law therefore followed the forum state's conflict rules.
Spencer Silver obtained a final federal judgment dismissing his state-law claim. Congress later passed a statute directing courts to reopen that exact judgment and enter relief for qualifying plaintiffs. The court refused to apply the statute because it targeted final judicial decisions rather than changing substantive law for pending cases.
Selena Singh sued Summit Bank in federal court and served process under a federal rule that differed from the state rule. The court applied the federal rule because it was valid under the Rules Enabling Act and did not abridge any substantive right. The validity of service therefore turned on the procedural character of the federal provision.
Sofia Stern sued Sapphire Technologies in federal court for personal injuries and the defendant sought an order compelling a medical examination. The court issued the order under federal procedural authority even though state practice differed. The availability of the examination was treated as procedural rather than substantive.
The court asks whether applying the federal rule instead of the state rule would produce a materially different outcome in the litigation. If the state rule is outcome-determinative it is treated as substantive and must be followed.
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Choice-of-law rules are treated as substantive. A federal court sitting in diversity must apply the choice-of-law rules of the state in which it sits.
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Congress may change substantive law for non-final cases but may not direct federal courts to reopen and reinstate cases that have reached final judgment.
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Yes. A Federal Rule adopted under the Rules Enabling Act controls if it is arguably procedural, even if the state rule would produce a different result.
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If the substantive law treats fees as an element of damages they must be proved at trial. Otherwise they are sought by post-judgment motion under the federal rule.
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…U. S. 518, 535. If the opinion commits this Court to the position that the Congress is without power to declare what rules of substantive law shall govern the federal courts, that conclusion also seems questionable. The line between procedural and substantive law is hazy but no one doubts federal power over procedure. Wayman v.…