Also known as: substance vs procedure · substantive or procedural · substance/procedure · substantive law · procedural law · Erie distinction
Written by attorneys · grounded in primary & secondary sources — see below
A classification of legal rules as substantive when they define the rights and duties of parties or procedural when they regulate the conduct of litigation and judicial administration. Courts apply the distinction to decide whether state or federal law governs an issue in diversity cases under the Erie doctrine. When characterization is uncertain the balance-of-interests test weighs state and federal judicial interests to determine the applicable rule.
Sylvia Santos sues a defendant in federal court in State A after an accident in State B. No federal rule addresses the precise timing for raising a defense of release. The court weighs State A's strong interest in uniform application of its release-timing rule against the federal interest in flexible case management and applies the state rule.
Sierra Santos prevails on a contract claim in federal court. She files a post-judgment motion for attorney's fees under a state statute that treats fees as an element of damages. The court requires the motion because the federal rule classifies the request as procedural rather than substantive.
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Stella Shapiro sues in federal court in State A on a contract formed in State B. The court applies State A's substantive rules on contract formation and performance because Erie requires federal courts to use state substantive law in diversity cases.
Sebastian Santos brings a tort claim in federal court in State A arising from events in State B. The court applies State A's choice-of-law rules to select the governing substantive law because those rules are treated as substantive for Erie purposes.
Sofia Stern obtains a final federal judgment dismissing her claim. Congress later passes a statute directing courts to reopen and reconsider only her case. The court refuses to reopen because the statute attempts to alter a final judicial determination.
Solomon Silver serves process on a defendant in a diversity case by leaving papers at the defendant's home with a resident of suitable age. The court upholds service under the federal rule even though state law requires personal delivery because the federal rule is valid and procedural.
The court applies the balance-of-interests test. It weighs the state's interest in having its rule applied against the federal judicial system's interest in uniform procedure. If the state interest predominates the federal court follows the state rule.
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Choice-of-law rules determine which state's substantive law governs the parties' rights and liabilities. Federal courts therefore follow the forum state's choice-of-law rules to avoid forum shopping and inequitable administration of the laws.
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A valid federal rule adopted under the Rules Enabling Act controls if it is arguably procedural. The rule governs even if it produces a different outcome from the state rule because the federal rule regulates the process of litigation rather than the underlying substantive rights.
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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.…