In an otherwise unbearable-to-read decision in Utility Air Regulatory Group v. EPA, Justice Breyer treated us to a citation of the Case of the Speluncean Explorers (a favorite of mine) and a discussion of cessante ratione legis cessat ipse lex.

Legal philosophers like to point out that a statute providing that “‘[w]hoever shall willfully take the life of another shall be punished by death’” need not encompass a man who kills in self-defense; nor must an ordinance imposing fines upon those who occupy a public parking spot for more than two hours penalize a driver who is unable to move because of a parade. See Fuller, The Case of the Speluncean Explorers, 62 Harv. L. Rev. 616, 619, 624 (1949); see also United States v. Kirby, 7 Wall. 482, 485–487 (1869) (holding that a statute forbidding knowing and willful obstruction of the mail contains an implicit exception permitting a local sheriff to arrest a mail carrier). The maxim cessante ratione legis cessat ipse lex—where a law’s rationale ceases to apply, so does the law itself—is not of recent origin. See, e.g., Zadvydas v. Davis, 533 U. S. 678, 699 (2001) (citing 1 E. Coke, Institutes *70b); Green v. Liter, 8 Cranch 229, 249 (1814) (Story, J.) (“cessante ratione, cessat ipsa lex”).

Now, don’t ask me to explain the rest of the opinion, because I can’t.