The European Court of Justice has issued guidance on the consequences of a Member State putting an aid measure into effect before it has been approved by the Commission. This follows a preliminary reference from the Austrian national court which arises out of domestic litigation concerning a 2006 Green Electricity Law granting state support for combined heat and power plants in Austria. The legislation in question had not been notified to the Commission, although the Commission had subsequently decided not to raise objections to it on the basis that it complied with the Community guidelines on state aid for environmental protection. The amount of aid granted to one of the plant operators, Wienstrom, by the Austrian state under this legislation was the subject of domestic legal proceedings.

In its ruling the ECJ noted that the questions referred to it essentially concerned the putting into effect of a measure prior to a positive decision of the Commission as to a measure's compatibility with common market state aid rules. The question for the ECJ was whether the prohibition on putting state aid into effect contained in Article 88(3) of the EC Treaty requires a national court to dismiss any action where a recipient of state aid seeks to recover aid for period pre-dating the Commission's approval of the applicable national legislation.

The ECJ ultimately concluded that a national court is not obliged to dismiss such an action.