The relationship between public international law and the domestic law of the Kingdom of the Netherlands is deeply rooted in the monistic tradition. According to the Dutch Constitution self-executing provisions of treaties and of resolutions of international organizations are binding upon natural and legal persons and have supremacy over national law, including the Constitution itself, Acts of Parliament and subordinate legislation. In this article the ways in which the Dutch courts deal with self-executing provisions, non-self-executing provisions and rules of customary international law are explored. For a long time the developments in the relationship between international and Dutch law have been dominated by the question of how to balance the separation of powers and the duty of the courts to apply public international law. But since the 1990s yet another problem has been gaining attention. There is growing concern about the question whether legal and natural persons are adequately protected by the Constitution against instruments of public international law (such as, for instance, decisions by UN sanctions committees) which may interfere with their basic rights, such as the right to a fair trial.