Difficult. The EU only exists since 1993, the precursor org was teh EEC. It seem the parliament exists since 1952 has direct elections since 1975, but a EU constitution does not exist yet (abandonded proposal in 2004 -- justly so, in my opinion).
One word: It's a terrible mess. And I'd argue it's not really democratic, but rather an instrument for the executive of the member countries to acquire legislative powers.