Institutional seats of the European Union are based in Luxembourg City along with the European Investment Bank. The Economic and Social Committee and the Committee of the Regions are entirely based in Brussels while the European Central Bank is based in Frankfurt and Europol is the only agency to have its seat fixed by the treaties, in The Hague. Separately, the Treaty of Nice establishes Brussels as the venue for all formal summits of the European Council after 2004. However some extraordinary sessions are sometimes held outside the city. The European Council's seat is however fixed by a declaration rather than a protocol, meaning it is
European Union member states acting alone). Laws made by the EU institutions are passed in a variety of forms. Generally speaking, they can be classified into two groups: those which come into force without the necessity for national implementation measures (regulations) and those which specifically require national implementation measures (directives). The European Union has seven principal decision making bodies, its institutions: the European Parliament, the European Council, the Council of the European Union, the European Commission, the Court of Justice of the European Union, the European Central Bank and the European Court of Auditors. Competence in scrutinising and amending legislation is shared