A central point of contention in the debate over same-sex marriage is the importance of preserving tradition. The Article on which this post is based evaluates the role of tradition as a justification for laws challenged on equal protection grounds, focusing on laws that limit marriage to opposite-sex couples.1 The Article makes two main points. First, a state’s interest in preserving tradition, including the tradition of opposite-sex marriage, is probably sufficiently legitimate to survive the most deferential standard of rational basis scrutiny under the Equal Protection Clause. Second, although preserving tradition is not illegitimate per se, courts should nonetheless view tradition as a suspicious justification. Features of tradition that counsel skepticism include its speculative utility, rhetorical appeal, and manipulability. Additionally, tradition is especially suspicious when offered to justify laws that burden a group toward whom there has been a cultural shift from widespread societal disapproval in the past to substantial public tolerance today. In such circumstances, tradition may serve opportunistically as a justification for people who are actually motivated by now-repudiated attitudes toward the burdened group. For bans on same-sex marriage, courts should invalidate such laws unless, after careful scrutiny, courts are satisfied that the laws are motivated by legitimate, non-tradition-based interests.