Law which governs the original rights and obligations of individuals. Substantive law may derive from the common law, statutes, or a constitution. For example, a claim to recover for breach of contract or negligence or fraud would be a common law substantive right. A state or federal statute giving an employee the right to sue for employment discrimination would also create a substantive right. Additionally, Sibbach v. Wilson (1941) illustrates how courts might approach the question of whether a law is substantive. There, the U.S. Supreme Court, in ruling that an order for a party to undergo a medical examination was a procedural and not a substantive matter, placed weight on the fact that no such substantive right existed in the common law and that no such statute touches on the matter.
Substantive law is contrasted with procedural law. However, the distinction is not always clear. Federal courts have struggled with the question of whether a law is substantive or procedural, as that question often determines whether state or federal law in diversity jurisdiction cases applies under the Erie Doctrine (which requires federal courts to apply state laws for matters of substantive law). To determine whether a law is substantive, federal courts may consider whether the law has the potential to determine the outcome of the litigation. For example, in Guaranty Trust Co. v. York, the U.S. Supreme Court was concerned with whether disregarding a state statute of limitations would significantly alter the outcome of litigation and held that statutes of limitations are substantive law. Specifically, the Court stated that “[t]he outcome of the litigation in the federal court should be substantially the same. . . as it would be if tried in a State court.” Subsequent courts have narrowed this analysis, focusing on whether applying federal procedural law to an issue would determine the outcome in light of its potential impact on forum shopping and inequitable administration of the laws—i.e. the aims of the Erie Doctrine. In Hanna v. Plumer, the U.S. Supreme Court ruled that the federal rules of service trumped the state’s requirement of in-hand service for the type of claim because the federal rule in question was arguably procedural and the federal service rule would not have affected the forum choice ex ante.
[Last updated in May of 2021 by the Wex Definitions Team]