Historically the US Citizenship and Immigration Services insisted that heterosexual marriages were the only ones that counted for immigration purposes meaning that only a heterosexual partner could petition for a green card for their foreign spouses.
Since Section 3 of the DOMA (Defense Of Marriage Act) was declared unconstitutional by the Supreme Court, the Secretary of Homeland Security has stated that same sex married couples will now be equally treated for immigration purposes and this is so even if the couple plans to reside in a non recognition state later on.
The USCIS has already begun providing green cards for legally married same sex couples that filed their application prior to the Supreme Court decision. Also, USCIS will reopen and reconsider petition that were submitted before the Supreme Court decision and denied at that time on behalf of the Section 3 of the DOMA. The same process will be conducted concerning work authorizations that were denied for the same reason.
The USCIS also added a “frequently asked questions” section on their website in order to give some clarity to same sex married couples that are considering petitioning for a green card.
Please visit the USCIS website for more detailed information: http://www.uscis.gov/family/same-sex-marriages.