Lambda Legal is taking aim at Social Security rules that block LGBTQ spouses from claiming survivor benefits because they weren’t able to legally wed before their partners died.

The latest federal lawsuit, filed on behalf of a 63-year-old gay man in U.S. District Court for the District of New Mexico, contends that the Social Security Administration (SSA) has set an impossible standard for many queer couples. That’s because the administration has a nine-month marriage requirement for social security survivor’s benefits, and some spouses died without ever being legally able to wed.

Thursday’s lawsuit is the third Lambda has hit SSA with over the nine-month rule. Two others are pending in Washington and Arizona.

The New Mexico case revolves around Albuquerque resident Anthony Gonzales, whose husband Mark Johnson succumbed to cancer just six months after the couple wed.

According to court documents, Gonzales and Johnson met and fell in love in 1998 and moved in together that December. Despite not being able to marry, they lived as spouses until Johnson died. They opened a joint checking account in January 1999, and the wrote each into their wills. Johnson designated Gonzales as his power of attorney.

The couple married on the first day they could as part of a mass wedding at Albuquerque’s Civic Plaza on August 27, 2013.

“We were together for 15 years, and we got married as soon as humanly possible, but I’m still barred from receiving the same benefits as other widowers, even though my husband worked hard and paid into the social security system with every paycheck,” Johnson said in a statement. “The government tells me we weren’t married for long enough, but we literally married the first day we could. How is that fair?”

Court documents note that Gonzales was with Johnson throughout his treatment for cancer, working from home and caring for him until he died on February 19, 2014.

“I held Mark’s hand as he took his last breath and died at 3:35 am,” Gonzales says in a court declaration.

Among other things, the suit argues that the denial violates the constitutional promise of equal protection under the law, disregards key Supreme Court marriage equality rulings, and constitutes sex discrimination.

“His exclusion from survivor’s benefits lacks even a rational basis,” the complaint reads. “Requiring Mr. Gonzales to have married Mr. Johnson when it was legally impossible for same-sex couples to do so in New Mexico is disconnected from any government interest.”

The complaint states that Gonzales has been denied $1,500 in monthly benefits for more than three-and-a-half years. It claims that an SSA judge urged Gonzales to challenge the rule.

“These benefits are as essential to the financial security of surviving same-sex spouses in their retirement years as they are to heterosexual surviving spouses,” said Lambda Legal Counsel Peter Renn in a statement. “But the government is holding their benefits hostage and imposing impossible-to-satisfy terms for their release.”

SSA declined to comment on the pending litigation.

In September, Lambda Legal hit SSA with a similar complaint on behalf of Washington resident Helen Thornton, whose partner of 27 years died in 2006, well before marriage equality took effect there in 2012.