Ian Ayres, professor at Yale Law School, continues his American Contract Law course with a segment on formation defenses, focusing on illegality as a bar to enforcing a promise. He works through Sinnar v. Le Roy, a case involving a bribe paid to secure a liquor license, using it to test when courts will refuse to enforce an agreement because of the unlawful conduct behind it. Ayres walks through the reasoning courts use to separate illegal bargains from otherwise valid contracts, and what happens to money or benefits already exchanged when a court finds illegality. The lecture is short and case-driven, part of a series originally recorded for Ayres' Coursera course on American Contract Law, and assumes some familiarity with the course's broader treatment of contract formation and defenses.