Sodomy in the legal sense is sex that is a crime. In Europe, North America, and South America, sodomy laws have been repeatedly struck down and barely survive in select quarters.  Therefore, same-sex partners do not commit sodomy once married. Neither do the heterosexuals who freely engage in such acts without censure from anyone. 

The sin of Sodom in the story of Sodom and Gomorrah had nothing to do with loving and consensual same-sex relationships. That "sodomy laws" have their basis in this story has more to do with the general obsession over a certain kind of sex act than the Sodom and Gomorrah story itself.