Economists and historians have long debated how open-access areas, frontier regions, and customary landholding regimes transformed into private property. This paper analyzes decentralized enclosure processes using the theory of aggregative games, examining how population density, enclosure costs, potential productivity gains, and local governance capacity, including the power to demand compensation, jointly determine the mix of property regimes. Depending on these fundamentals, private decisions to enclose may be strategic complements or substitutes. Strategic complements generate tipping points and socially destructive property races, whereas strategic substitutes produce smoother transitions and may leave enclosure below the social optimum. While policies to strengthen customary governance or compensate displaced stakeholders can realign incentives, addressing one distortion while neglecting others can worsen welfare.