The Scriptures teach us that people have always been fearful of immigrants. Pharaoh, confronting a fast-growing population of Israelites, enslaved them and instituted the first documented population-control policies. Once settled in their own country, the Israelites themselves forgot the honor due to foreigners, even though each of the patriarchs had been a sojourner in a country not his own. Consequently, the Torah reminds the Israelites that they should treat sojourners as well as they treat their own people. Immigration is always a controversial subject. Catholic social teaching maintains that there is a right to migrate. But what does this mean, especially in societies saturated in “rights-talk?” This monograph explains the nature, origins and limits of the right to migrate, and illustrates some of its policy-implications.