Recent work in both the theory of the firm and of corporate law has called into question the appropriateness of analysing corporate law as ‘merely’ a set of standard form contracts. This article develops these ideas by focusing on property law’s role in underpinning corporate enterprise. Rights to control assets are a significant mechanism of governance in the firm. However, their use in this way predicates some arrangement for stipulating which parties will have control under which circumstances. It is argued that ‘property rules’—a category whose scope is determined functionally—protect the entitlements of parties to such sharing arrangements against each other’s opportunistic attempts to grant conflicting entitlements to third parties. A...