Municipal liability under §1983 must be based on enforcement of a municipal policy or practice. The policy may be a formally adopted policy such as an ordinance or regulation, a custom or practice that is so persistent and well settled as to have the force of law, or the final decision of an official who has policymaking authority. Monell v. NYC Dep't of Social Services, 436 U.S. 658, 690 (1978). This column focuses on municipal customs and practices.