The Court of Justice of the European Union (CJEU) is an institution of the European Union (EU).  It is responsible, inter alia, for ensuring that EU law is interpreted and applied in a consistent way in all EU countries.  If a national court is in doubt about the interpretation or validity of an EU law, it can ask the Court for clarification.  The same mechanism can be used to determine whether a national law or practice is compatible with EU law.  The CJEU also resolves legal disputes between national governments and EU institutions, and can take action against EU institutions on behalf of individuals, companies or organisations.