The VA had said its regulations defined a spouse as "a person of the opposite sex" despite a U.S. Supreme Court ruling in June validating marriage between people of the same sex, NBC News reported Friday.
Tracey Cooper-Harris, a 12-year Army veteran, had filed suit against the VA after the agency refused to recognize her 2008 marriage, causing her to receive $124 a month less in disability payments than a veteran in an opposite-sex marriage.
The VA is dealing with several similar lawsuits after it said the Supreme Court ruling didn't apply to it.
VA Secretary Eric Shinseki has said the court did not specifically strike down a federal regulation defining a spouse as someone of the opposite sex, so it would continue to apply the rule.
Late Thursday, U.S. District Judge Consuelo Marshall of Los Angeles ruled that portion of federal law was made unconstitutional "under rational basis scrutiny."
Marshall approved an injunction permanently barring the VA from using the regulation, saying the denial of benefits to same-sex spouses "is not rationally related" to military purposes.
Cooper-Harris served in Iraq before receiving an honorable discharge in 2003. She suffers from multiple sclerosis and receives $1,478 a month in VA disability, the amount an unmarried veteran would receive.