This paper attempts to define what we call the liberal script of borders, i.e. normative ideas that arise from liberalism and regulate cross-border interactions. We divide cross-border interactions into four categories: communication and the exchange of information, economic transactions in the form of trade and investments, the movement of people in the form of emigration and immigration, and finally, the cross-border use of force in the form of military intervention. We argue that the liberal border script is characterized by an inherent tension between individual and collective self-determination. However, as the right to collective self-determination is based on the principle of individual self-determination (as the normative core of liberalism), liberal thought gives priority to the right to individual self-determination. Thus, the main thrust of the liberal border script is to limit state discretion regarding border control in light of the universal right of individuals to cross-border interactions. International law provides a reasonable point of reference to determine the specific institutionalized content of the contemporary border script, although not everything that is enshrined in international law can be interpreted to be liberal. We analyze how international law regulates the four kinds of cross-border interactions identified above. This yields the following conclusions: (1) The right of the state to interfere with the communication and exchange of information across national borders is very limited. (2) Most states of the world have agreed to substantially limit their ability to interfere with the flow of trade and capital across their borders. (3) States retain the right to control immigration, but under international human rights law they are required to open their borders to emigrants as well as to refugees and asylum seekers who flee from persecution. (4) Nation states monopolize the use of force on their territory; the possibility for other states to intervene militarily remains extremely limited. In addition, we point out for each of the four domains how the liberal elements of the border script are currently being enforced by strengthening the principle of individual self-determination, and how they are contested by emphasizing collective self-determination.