EASA is an agency of the EU, established by directive EC 1592/2002, superseded by EC 216/2008. Non-EU members states are treated as 'Third Countries' which can use the EASA certification system but have no membership of the management board, hence no say in making the rules. Switzerland, Norway and Iceland are not EU members but are part of the European Economic Community (EEC) and, as such, are subject to most EU laws (including free movement across borders). It will be interesting to see how the UK-EU relationship develops, with the UK as a Third Country in the eyes of EASA........