This article starts with a critical reflection on John Westlake’s reading of the history of empire and the English/British East India Company – for him, essentially, the proper concern of ‘constitutional history’ rather than international law. For Westlake, approaching this history through the prism of nineteenth-century positivist doctrine, the Company’s exercise of war powers could only result from state delegation. Against his warnings to international lawyers not to stray from the proper boundaries of international legal inquiry, the article proceeds to recover Hugo Grotius’s theory of corporate belligerency in his early treatise De iure praedae. For Grotius, corporations could wage public war on behalf of the state yet, at the same time, were in law capable of waging private war in their own right. The article proceeds to reflect on the practice of corporate belligerency in the centuries separating Westlake and Grotius; it concludes with observations on the implications of Grotius’s theory of corporate belligerency today.