The case of Erie Railroad v. Tompkins has wrought a great change in the relationship between the state and federal courts. Prior to its decision, the federal courts under the rule of Swift v. Tyson did not have to apply the state non-statutory law. They could apply their own notions as to what the law was in matters of general law relating to substance. The Conformity Act compelled the federal courts to follow the practice, pleading, and forms and modes of proceeding in like causes in the courts of the state within which the federal district courts were held. In other words, under the Conformity Act and the rule of Swift v. Tyson, the federal courts in matters not covered by statute were free to apply their own rules as to substantive law, but had to follow the state courts in procedural matters.
John H. Uhl,
FEDERAL COURTS - SUBSTANCE AND PROCEDURE - EFFECT OF ERIE RAILROAD V. TOMPKINS AND RULE 8 (c) OF THE FEDERAL RULES OF CIVIL PROCEDURE UPON BURDEN OF PROOF OF CONTRIBUTORY NEGLIGENCE,
Mich. L. Rev.
Available at: https://repository.law.umich.edu/mlr/vol37/iss8/5