Such dynamic developments are surprising in light of the legal and institutional conditions which existed in the late 1950s and 60s. Acting without any legislative authority, European policy-makers initially increased the EU's capacity to act by defining environmental policy as a trade problem. The most important reason for the introduction of a common environmental policy was the fear that trade barriers and competitive distortions in the Common Market could emerge due to the different environmental standards. However, in the course of time, EU environmental policy emerged as a formal policy area, with its own procedures. The legal basis of EU environmental policy was not more explicitly established until the introduction of the Single European Act in 1987.