In the colonial period of American history, the British Crown reviewed, and sometimes nullified, acts of colonial assemblies for “repugnancy to the laws of England.” In this way, Crown review established external, legal constraints on American legislatures. I present a formal model to argue that Crown legislative review counteracted political pressure on imperial governors from colonial assemblies, to approve laws contrary to the empire’s interests. Optimal review in the model combines both legal and substantive considerations. This gives governors the strongest incentive to avoid royal reprisal by vetoing laws the Crown considered undesirable. Thus, review of legislation for consistency with higher law helped the Crown to grapple with agency problems in imperial governance, and ultimately achieve more (but still incomplete) centralized control over policy. I discuss the legacy of imperial legislative review for early American thinking about constitutional review of legislation by courts.