THE IMPERIAL concepts of formal membership prior to the twentieth A century developed in parallel with the expansion of the British empire into a global institution. Under the common law principle of allegiance, it was by the unilateral decision of the imperial government that the concepts of formal membership were modified whenever a new group of people was included or excluded. It was also the imperial government which ultimately decided whether the status of British subjecthood could be granted through colonial legislation. In 1901, however, an interdepartmental committee published a paper recommending that the systems of colonial naturalization should be consolidated in such a way that their effects could be recognized throughout the empire.1 In establishing the system of imperial naturalization, the method of maintaining British subjecthood also changed, at least in the Dominions and Britain, where British subjecthood was granted on the grounds of the ‘common code’ (a set of statutory provisions which defined who were British subjects and in what circumstances this status was acquired or lost).2 Unlike in previous periods, the common code resulted from consultation and mutual agreement between the British and Dominion governments in the colonial (later, imperial) conferences-the conference system which had developed since 1887 among the self-governing parts of the empire.3 The common code was embodied by the British Nationality and Status of Aliens Act 1914 (BN & SA act 1914), and subsequently adopted by the Dominions.