It is possible to become a United States citizen by marrying someone who is already a legal resident? Before July 2013, this process was only available for married couples involving a man and a woman. However, when the Supreme Court decided that Section 3 of the Defense of Marriage Act (DOMA) was unconstitutional, everything changed. President Obama swiftly directed all federal departments to comply with the Supreme Court decision. From then on, the U.S. Citizenship and immigration Services (USCIS) has reviewed and accepted immigration visa petitions on behalf of same sex spouses just as they have for opposite-sex spouses in the past.
If you are a U.S. citizen or a lawful permanent resident who is currently in a same-sex marriage to a foreign national, your fiancé or fiancée will be able to apply to become a citizen once you have been married and living together for three years as long as all other requirements are met. The fact that you are in a same sex marriage will not affect your eligibility.