A railroad had given Mr. and Mrs. Mottley lifetime rail passes to settle a prior claim, but after a federal law made lifetime rail passes illegal, they stopped honoring them. The Mottleys sued in federal court for breach of contract.
Questions of law
What level of relatedness to a federal law is required for subject matter jurisdiction?
Although the Mottleys anticipated that the federal law would be brought as a defense, this anticipation did not satisfy subject matter jurisdiction in their claim, and it was remanded for state courts to handle.