What roles have lawyers played in the British immigration system? Have these roles made the system more just? This thesis tackles these questions by focusing on the doctrines and ideas of public law. Chapter 2 discusses 19th-century legal debates about immigration practices of the British colonies. It claims that there was a rough consensus about the need for legal limits not only to these practices but corresponding practices that might be adopted in Britain. Chapter 3 surveys the contemporary literature on immigration justice, isolating principles that are salient for the appraisal of public law doctrines. It also explains major changes that occurred to the legal order of immigration control across the 20th century. Chapter 4 deals with administrative law. It argues that this branch of public law has enhanced the degree to which immigration control facilitates democratic self-determination and has provided tools for resisting dangerous practices of immigration detention. But it has not constrained or even exposed the rationale for the government’s contentious control of economic immigration. Chapter 5 deals with human rights law. In the face of political risk, this branch of public law has protected many immigrants from unjustifiable deportation. In a curious role reversal, the interventions of human rights lawyers resemble the Home Office’s treatment of the criminal courts’ earlier practices of recommending immigrants for deportation. But more work must be done by human rights lawyers to connect the right to respect for private life with the integration and social equality of immigrants (including unauthorised immigrants) within the community. Chapter 6 deals with anti-discrimination law. It argues that lawyers have largely failed to undo the historical disapplication of this branch of public law to immigration control; one current feature of this legacy is the apparent lawfulness of the ‘hostile environment’. Chapter 7 reflects on the implications of immigration lawyers’ achievements for the constitution. It concludes that the supposed principle of aliens’ general vulnerability to exclusion and deportation, defended by John Finnis and assumed by other writers, needs qualification.