Rules of Decision Act (28 U.S.C. § 1652)
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.
Significance
The RDA is the statutory foundation of the Erie doctrine. In Erie Railroad Co. v. Tompkins (1938), the Supreme Court relied on the RDA (then § 34 of the Judiciary Act of 1789) to hold that federal courts in diversity cases must apply state substantive law, not general federal common law. The Court held that the pre-Erie practice under Swift v. Tyson (1842) of applying general federal common law to “general” questions was unconstitutional.
“Laws of the several states” includes state common law, not just statutes (Erie).
RDA vs. Rules Enabling Act
The RDA and the Rules Enabling Act (28 U.S.C. § 2072) interact in the Erie analysis:
- RDA commands application of state law as the rule of decision
- REA authorizes the Federal Rules of Civil Procedure, provided they do not “abridge, enlarge or modify any substantive right”
- When an FRCP directly governs, the REA track applies (Hanna v. Plumer Track 1)
- When no FRCP governs, the RDA/Erie analysis applies (Hanna Track 2)