From the 1880s, states and self-governing colonies in North and South America, across Australasia, and in southern Africa began introducing laws to regulate the entry of newly defined “undesirable immigrants.” This was a trend that intensified exclusionary powers originally passed in the 1850s to regulate Chinese migration, initially in the context of the gold rushes in California and the self-governing colony of Victoria in Australia. The entry and movement of other populations also began to be regulated toward the end of the century, in particular the increasing number of certain Europeans migrating to the United States. It is perhaps unsurprising, then, that Britain followed this legal trend with the introduction of the 1905 Aliens Act, although it was a latecomer when situated in the global context, and certainly within the context of its own Empire. The Aliens Act was passed in response to the persecution of Eastern European Jews and their forced migration, mainly from the Russian Empire into Britain. It defined for the first time in British law the notion of the “undesirable immigrant,” criteria to exclude would-be immigrants, and exemptions from those exclusions. The Aliens Act has been analyzed by historians and legal scholars as an aspect of the history of British immigration law on the one hand, and of British Jewry and British anti-Semitism on the other. Exclusion based on ethnic and religious grounds has dominated both analyses. Thus, the Act has been framed as the major antecedent to Britain's more substantial and enduring legislative moves in the 1960s to restrict entry, regulate borders, and nominate and identify “undesirable” entrants effectively (if not explicitly) on racial grounds.