Immigrating into the United States is difficult. Recognizing the value and importance of intact families, the law allows U.S. citizens to sponsor their spouses, making them eligible for so-called green cards, which allow them to live and work in the United States permanently.
Not so for same-sex couples. In most states, same-sex couples aren’t permitted to marry. But even in states where full marriage equality has been achieved, the immediate family member option isn’t available as a way of (re)uniting same-sex couples — because, again, thanks (no thanks) to DOMA. Because immigration law is federal, DOMA applies, and it declares same-sex marriages null and void.