This article examines a key ambiguity in the Opium War treaties of 1842-1843, which concerned the legal status of Hong Kong’s native Chinese population. Overlooked in existing studies, the question was whether the cession of Hong Kong entailed British jurisdiction over crimes involving Chinese people inter se. To British minds, the idea of territorial sovereignty pulled against the reciprocal premise of the treaties, by which China and Britain enjoyed an absolute right to discipline their own offenders. To square the circle, British officials mooted various compromises steeped in extant ideas of sovereignty and subjecthood. Subsequently, all efforts at a principled policy were abandoned following a pivotal murder in eastern Hong Kong. Seven Chinese suspects were examined at the colonial magistracy for possible surrender to China, but the hearing was construed after the fact as a full trial and acquittal, which anchored exclusive British jurisdiction on the island. Thus, Hong Kong lay at the intellectual centre of Britain’s incipient Chinese Empire. The meaning of the Opium War treaties was shaped through iterative domestic discourse, in which the ideas of territorial sovereignty, extradition, and extraterritoriality were mutually constitutive, and law-making involved the retrospective rationalization of equivocal events and decisions on the ground.