⚡ 10-Second Rule
A federal court hearing a state-law case borrows state law for who wins and keeps its own rules for how the trial runs.
🧒 ELI-10 Scene
Nadia sleeps over at her cousin Omar's house, and they play Monopoly. Omar's family has house rules about scoring. Those house rules decide who wins the game. But Nadia still brushes her teeth her own way, in her own order. Nobody at Omar's house can change her routine. The winning rules belong to the house she's visiting. The routine belongs to her. A federal court is Nadia: borrowed rules for who wins, its own routine for getting there.
⚖️ Actual Rule
The Rules of Decision Act, 28 U.S.C. § 1652, provides: "The laws of the several states, except where the Constitution or treaties of the United States or Acts of Congress otherwise require or provide, shall be regarded as rules of decision in civil actions in the courts of the United States, in cases where they apply." In Erie Railroad Co. v. Tompkins, 304 U.S. 64 (1938), the Supreme Court held that "[t]here is no federal general common law," so a federal court sitting in diversity applies state substantive law and federal procedural law. Hanna v. Plumer, 380 U.S. 460 (1965), created two tracks. Track one: if a Federal Rule of Civil Procedure directly covers the issue, the federal court applies it so long as it is valid under the Rules Enabling Act, 28 U.S.C. § 2072 — meaning it really regulates procedure and does not "abridge, enlarge or modify any substantive right." Track two: if no federal directive is on point, the court makes the "relatively unguided Erie choice," applying the outcome-determination test of Guaranty Trust Co. v. York, 326 U.S. 99 (1945), read through Hanna's twin aims — discouraging forum shopping and avoiding inequitable administration of the laws. Byrd v. Blue Ridge Rural Electric Cooperative, 356 U.S. 525 (1958), adds that strong countervailing federal interests, such as the federal allocation of power between judge and jury, can outweigh a weak state interest.
ELI-10 translation: use state law for the real rights, federal rules for courtroom mechanics, and check which track you're on first.
🔍 Ask These Questions
- Is the federal court deciding a state-law claim, usually in diversity? (Is the court a visitor playing someone else's game?)
- Does a federal directive — the Constitution, a federal statute, or an FRCP — directly answer the disputed question? (Does a federal rule already sit exactly on this spot?)
- If yes, is the Federal Rule valid under the Rules Enabling Act? (It almost always is — the Supreme Court has never struck one down — so the Federal Rule wins.)
- If no federal rule is on point, would using a federal practice change outcomes and invite forum shopping? (Would picking the federal courthouse change who wins? Then borrow the state rule.)
- Check the classic substantive list: claim elements, statutes of limitations and their tolling rules, burdens of proof, choice-of-law rules. (Time limits and who-must-prove-what always belong to the state.)
- Any Byrd wrinkle? (Sometimes the federal house cares so much — like letting juries decide facts — that it keeps its own way.)
⚠️ Bar Trap
Exam language: Examiners present a conflict squarely governed by a Federal Rule of Civil Procedure and bait you into running an outcome-determinative or forum-shopping analysis, when Hanna makes the valid Federal Rule controlling. The mirror trap: a state statute of limitations sounds procedural, but for Erie purposes it is substantive, and under Walker v. Armco Steel Corp., 446 U.S. 740 (1980), FRCP 3 does not displace a state rule on when an action is commenced for tolling purposes.
ELI-10: First ask if a federal rule already sits on the exact spot. If it does, stop — it wins. And don't be fooled by time limits: deadlines to sue belong to the state, even though they sound like mechanics.
🧪 Question
A carpenter sued a lumber supplier in federal district court, invoking diversity jurisdiction, for breach of a supply contract governed by state law. The state's statute of limitations for contract actions is four years, and a companion state statute provides that an action is commenced for limitations purposes only when the defendant is served with process. The carpenter filed the complaint three days before the four-year period expired but did not serve the supplier until five weeks later. The supplier moved for summary judgment on limitations grounds, and the carpenter responded that Federal Rule of Civil Procedure 3, which states that a civil action is commenced by filing a complaint, controls.
How should the court rule?
(A) For the supplier, because the state service rule is an integral part of the state limitations scheme and no Federal Rule governs tolling of a state statute of limitations. (B) For the carpenter, because Rule 3 directly conflicts with the state rule and a valid Federal Rule always displaces state law. (C) For the carpenter, because rules governing commencement of an action are procedural and federal courts apply federal procedural law. (D) For the supplier, because state law governs every question in a diversity case.
Answer: (A). Under Walker v. Armco Steel Corp., Rule 3 marks the start of the federal procedural clock but does not purport to toll a state statute of limitations, so there is no direct conflict. With no Federal Rule on point, the state service-based commencement rule — bound up with the substantive limitations period — applies, and the action is time-barred.
💡 Why the Wrong Answers Are Wrong
- (B) assumes a direct collision; Rule 3 was read narrowly and never addresses tolling, so the Hanna rule-on-point track never engages.
- (C) mislabels the rule; commencement here operates as part of the limitations period, which is substantive for Erie purposes.
- (D) overshoots in the other direction; federal courts in diversity still apply federal law to genuinely procedural questions.
- ELI-10: The misconception is skipping the first question. Always ask whether a federal rule truly covers the exact spot before doing any balancing.
