What are the CJEU’s powers? ‘Enforcing EU law’ considers three of the most important. Infringement proceedings assess claims by the Commission that Member States have failed to do what the Treaties require of them. If such a claim is successful, financial sanctions may be imposed on the State concerned. The action for annulment allows the validity of EU acts to be challenged and enables the CJEU to ensure that the other institutions act within the limits of their powers. The preliminary rulings procedure is the ‘keystone’ of the judicial system established by the Treaties and involves helping national courts to apply EU law correctly.