IN 1996, a San Antonio window washer named Jonathan Littleton died at 35 of a misdiagnosed blood clot. His wife, Christie Lee Littleton, filed a medical malpractice suit under a statute accessible only to surviving spouses.

Ms. Littleton was born male, but identified as female even as a child. At 28, she underwent full sex reassignment surgery at a Texas university hospital. Her sex was changed to female on her birth certificate and driver’s license. She and her husband later obtained a marriage license without incident.

But in a pretrial motion, defense attorneys in the case of Littleton v. Prange claimed that because Ms. Littleton had been born male, she was a man and therefore could not be another man’s spouse. Two years earlier, Congress had passed the Defense of Marriage Act, defining marriage as a union between one man and one woman. The judge ruled that Ms. Littleton had no standing to bring the suit. An appeals court, referencing DOMA and the immutability of chromosomes, upheld the verdict. Further appeals were denied.

The Littletons didn’t see themselves as being in a same-sex marriage. But the courts disagreed. Laws against same-sex marriage have often been used as a barrier to marriage rights for heterosexual transgender people, although the two should never have been conflated. Now that the Supreme Court’s June ruling in Obergefell v. Hodges makes same-sex marriage a federal right, courts need to resolve related matters for transgender litigants. They should adhere to the principle, which to date has not been universally recognized, that a marriage remains valid until death, divorce or annulment, regardless of whether a spouse changes gender.