Same-sex marriage is not illegal in the United States. It is legal in some states, but not in others. On the federal basis, it is legally recognized, except that for some purposes, the couple may have to reside in a state that recognizes their marriage. In states where same-sex marriage is not legal, it is not legal because of the state marriage statute or, in some cases, because of an amendment to the state constitution.

Some states and countries have legalized same-sex marriage. Some states and countries have banned same-sex marriage by statute and some by amending their constitutions.

Same-sex marriage is already legal on the federal level in the United States. However, since marriage has always been controlled by state law, the legality of entering into a same-sex marriage varies from state to state. Currently, some states permit same-sex couples to marry, but most do not. The number of states permitting and recognizing same-sex marriages continues to grow slowly. It is likely that same-sex marriage will eventually become legal in all 50 US states, although that may be many years from now.

In the United States, there is no amendment to the federal Constitution that opposes same-sex marriage. Many states, however, have adopted amendments to their individual state constitutions that prohibit same-sex marriage.

Yes, as of October 7, 2014 same-sex marriage in Nevada became legal.