There are 10 countries in which gay marriage is legal. The Parliament of The Netherlands, which passed a bill legalizing same sex marriage by a 3-to-1 margin in 2001, was the first national government body to pass national legislation.Since then, another nine countries have followed suit.he Parliament of The Netherlands, which passed a bill legalizing same sex marriage by a 3-to-1 margin in 2001, was the first national government body to pass national legislation. Since then, another nine countries have followed suit.