The American and some other constitutions entrench property rights by requiring super majoritarian voting amending or revoking their own provisions. Following Buchanan and Tullock , this paper analyzes individuals' interests behind a veil of ignorance, and shows that under some standard assumptions, a (simple) majoritarian rule should be adopted. This result changes if one assumes that prefer- ences are consistent with the behavioral phenomenon known as the endowment effect." It then follows that (at least some) property rights are best defended by super majoritarian protection. The paper then shows that its theoretical results are consistent with a number of doctrines underlying American Constitutional Law.