"Immigration has become a hot-button issue that stands at the forefront of public debates. This project addresses a simple but important question: Is it legally and morally defensible for a liberal state to restrict migration in order to preserve cultural rights of a majority group? This question is one of the greatest challenges facing liberalism today. It is fiercely debated in the U.S. Congress, EU institutions, and international organizations.""Cultural Defense"" discusses the justifications and limits of cultural rights of majority groups from a liberal perspective. On the whole, it accepts that some cultural restrictions on migration can be legitimate, but only if culture is defined very narrowly. The project constructs a liberal theory of the right of a majority to preserve fundamental essentials of its culture—its Britishness, Frenchness, Germanness, etc.—without recourse to the draconian measures recently adopted in several states. In so doing, the project attempts to square the circle; it provides a new theory in which liberal states can welcome migrants without dramatically changing the cultural makeup of their society.The project contains five parts. The first characterizes contemporary patterns of global migration and shows that it presents a new challenge. The second finds that, as a result, liberal states have become obsessive with their national culture. Citizenship is undergoing a process of ""cultural convergence"" under which liberal states define the essence of their citizenship, and thereby the rules of joining the community, in cultural terms. The third describes why this process embraces illiberal policies that violate the same values it seeks to protect. The fourth sets out a liberal theory of cultural defense, exploring its justifications and boundaries in human rights law and moral philosophy. The fifth part develops a workable metric—termed ""National Constitutionalism""—distinguishing legitimate cultural restrictions from illegitimate ones."