Educational diversity arose as a shared valuable resource benefitting both universities and students in two landmark affirmative action cases — Regents of the University of California v. Bakke and Grutter v. Bollinger. This Article argues that diversity empirically resembles a commons (i.e., a shared resource). Extending this analysis exposes plaintiffs who file anti-affirmative action lawsuits — individuals like Abigail Fisher in Fisher v. University of Texas — as agents of enclosure who are trying to enclose the educational diversity commons, destroy its management structure, and privatize it for their own benefit (i.e. to gain admission into elite universities). Examining diversity and affirmative action through a common property lens reveals that the defense of race-conscious admissions policies faces a collective action problem. The interests of universities and their minority students largely overlap in their desire to protect diversity. They diverge, however, when universities refuse to employ additional equality rationales that could strengthen the defense of diversity and race-conscious admissions. This refusal facilitates anti-affirmative action efforts.