There are ten European countries (in red) which have constitutional bans prohibiting recognition or legalization of same-sex marriage: Belarus, Bulgaria, Hungary, Latvia, Lithuania, Moldova, Montenegro, Poland, Serbia and Ukraine. Half of these countries (Bulgaria, Hungary, Latvia, Lithuania and Poland) ARE members of the European Union.
It will be interesting to see how the European Union will resolve the question of marriage equality. I would guess that the EU will have uniform laws recognizing same-sex couples well before the United States does.
Hat/tip to Joe.My.God