Over the nearly four decades it has been in print, Reason in Law has established itself as the place to start for understanding legal reasoning, a critical component of the rule of law. This ninth edition brings the book's analyses and examples up to date, adding new cases while retaining old ones whose lessons remain potent. It examines several recent controversial Supreme Court decisions, including rulings on the constitutionality and proper interpretation of the Affordable Care Act and Justice Scalia's powerful dissent in Maryland v. King. Also new to this edition are cases on same-sex marriage, the Voting Rights Act, and the legalization of marijuana. A new appendix explains the historical evolution of legal reasoning and the rule of law in civic life. The result is an indispensable introduction to the workings of the law.