This special issue looks at the normative implications of EU global regulatory efforts in the area of environmental policy. The EU Environmental Emissions Trading System (EU-ETS) represents an example of successful application of EU environmental standards where global standards harmonization had failed. The intersection between EU law and global law, however, seems increasingly porous and difficult to decipher. Post-Lisbon, the EU increasingly functions like a State in its actions with the world. Nonetheless, the operation of international law internally within the EU legal order has been the subject of many distinctive constitutional periods, both prior to and after the Treaty of Lisbon. In the recent judgment of the Grand Chamber of the Court of Justice on the EU-Emissions Trading System, the Court rejected claims that the application of the EU-ETS scheme to the aviation sector, specifically US airlines, was unlawful under EU and international law. In the realm of the environment, EU environmental protection is both a value and normative aspiration. Yet what is a successful legal outcome of the adoption of ambitious and aggressive global legal regulatory frameworks in this domain? How should contemporary EU global policy and value ambitions be adjudicated in law? The case raises broader issues about the legitimacy of EU law and externalities arising from extended EU competences to positively promote EU constitutional values beyond Europe. While using this case as its starting point, this special issue sets out to look at the wider constitutional questions asked by it.