Andorra is not a member of most of the major European associations. Even though they use the Euro, they are not technically part of the Eurozone. They have a special relationship with the EU which they follow their trade rules for industry but not for agriculture. They are also not a party to the Schengen Treaty, however, you can only access Andorra via Spain and France which are party to the treaty and they don't have an airport, so no one worries about them.

More Info: everything-everywhere.com