As “Guardian of the Treaties”, one of the tasks entrusted to the European Commission by article 17 of the Treaty on European Union is to oversee the application of EU law. The infringement procedure – articles 258 to 260 of the Treaty on the Functioning of the European Union – is one of the enforcement mechanisms that can be applied by the Commission against a Member State whenever the Commission is of the opinion that the Member State is in breach of its obligations under European Union law.The objective of this seminar is to present a practical analysis of the infringement procedure with a view to improving the capacity and quality of responses to Commission investigations of potential infringements. This seminar provides a practical overview of the infringement procedures, the role of the Commission and the position of the Member States (e.g. how to avoid a Court case and possible defences).