This contribution analyses the influence of WTO primary and secondary law on the primary and secondary law of the European Union. Moreover, the influence of WTO panel and Appellate Body reports on EU secondary law and administrative decisions is evaluated. As a principal example the article takes the interaction between WTO and EU anti-dumping law. However, also other selected examples of the influence of WTO law on EU law are subjected to scrutiny. It turns out that WTO primary and secondary law have had a considerable influence on EU primary and secondary law and their interpretation. This is true in particular where the scope and the technical aspects of classical trade policy are concerned, ranging from the scope of the EU’s trade policy powers to the details of EU anti-dumping law. However, in respect of the EU’s internal regulatory policies, the WTO has had much less influence and the EU has been less law-abiding.