With reference to political philosophy, this chapter argues that the “liberal border script” is characterized by an inherent tension between individual self-determination, which includes the right to cross-border interactions, and collective self-determination, which covers the states’ right to control their borders. It further argues that international law provides a reasonable point of reference to determine the specific content of the current border script. It then analyzes how international law regulates three kinds of cross-border interactions (communication, economic transactions, and the movement of people) and to what extent this can be interpreted in terms of the liberal border script. The chapter demonstrates that the right of the state to interfere with communication across national borders is very limited (1), that most states have substantially limited their ability to interfere with trade (2), and that states retain the right to control immigration, but they are required to open their borders to refugees (3).