Through the joint ‘North Seas Countries Offshore Grid Initiative’ the states bordering the North Seas are establishing shared large-scale offshore electricity infrastructure in order to exploit their offshore wind energy resources. The article argues that this international governance of oceans space comes about legally because international law, European law and national law each fulfil a specific function. The climate regime provides the normative impetus, the law of the sea allocates competences, and European law contains principles of cooperation, which are then implemented through coordinated national law. International law, European law and national law thus become functionally integrated. This analysis has significance beyond shared offshore electricity infrastructure. It illustrates the way in which the functional integration of international law, European law and national law is emerging as a distinct legal institution in its own right, separate and distinct from the various legal orders themselves.