This paper analyzes the technique of consistent interpretation, one of the most common tools by which national courts give effect to international law. After describing the functions that consistent interpretation can conceivably perform in the domestic implementation of international law and clarifying its conceptual relationship to direct application, the contribution inquires into the legal bases of this judicial technique. Such legal bases, it is argued, do not lie in international law, which provides no directives to national courts on this matter. Instead, domestic courts justify their interpretive reliance on international law by resorting to domestic law rationales: notably, the presumed intent of the legislature, the domestic hierarchy of laws or the pursuance of relevant principles or values. It is shown that, in many respects, the extent and limits of consistent interpretation depend on which rationale a court relies on. On this basis, the study submits that the possibility to realize the potentials of consistent interpretation rests primarily on the courts' willingness to exploit the international law-friendly traits of national constitutions.