Poland became an associate member of the EU and its defensive arm, the Western European Union, in 1994. In a June 2003 national referendum, the Polish people approved EU accession by an overwhelming margin, and Poland gained full membership on May 1, 2004. | Poland became an associate member of the EU and its defensive arm, the Western European Union, in 1994. In a June 2003 national referendum, the Polish people approved EU accession by an overwhelming margin, and Poland gained full membership on May 1, 2004. |