This article examines the question to what extent the provisions of the Austrian Federal Constitution on the direct applicability of international treaties on the one hand and customary international law on the other can be regarded as “open” (or “friendly”) towards public international law. The question can, in principle, be answered in the affirmative for both constellations, even if direct applicability is of greater practical importance for international treaty law. On closer examination, the specific Austrian instrument of the “reservation of (statutory) implementation” for international treaties also proves to be an instrument that is potentially “friendly” to international law. Consequently, it can be concluded that, with regard to the direct applicability of international law, the Austrian constitution is “relatively” open (or “friendly”) towards public international law.
