Gay married couples in the US state of Massachusetts are suing the federal government for benefits received by straight married couples.
Currently, the Defence of Marriage Act 1996 prohibits the federal government from granting benefits, such as those relating to health insurance and pensions, to gay married couples.
The suit is being filed by the Gay and Lesbian Advocates and Defenders group, on behalf of eight couples and three widowers, some of whom are federal employees.
Others claim they are losing money through being barred from filing taxes jointly or are receiving less generous social security benefits.
Mary Ritchie, a Massachusetts State Police trooper, has been married to her partner Kathleen Bush for five years and has two children.
However, she estimates they have paid almost $15,000 (£10,600) more in taxes than a straight married couple, as they cannot file their federal tax income tax returns jointly.
“It saddens us because we love our country,” Ms Ritchie said.
“We are taxpayers. We live just like anyone else in our community. We do everything just like every other family, like every other married couple, and we are treated like less than that.”
Another plaintiff is Dean Hara, the spouse of former US Representative Gerry E Studds.
After Mr Studds died in 2006, Mr Hara, 51, was denied his Congressional pension and other benefits normally extended to surviving spouses of federal employees.
He said: ”I am not being treated the same as any other surviving spouse of any other federal employee or public servant who has served this country for 27 years, when I have been legally married.”
According to Mary Bonauto, GLAD’s civil rights project director, the lawsuit is the first major challenge to the section of the law that denies same-sex couples access to more than 1,000 federal programmes and legal protections in which marriage is a factor.
Same-marriage is currently legal in only in only two states, Massachusetts and Connecticut, which means the numbers of spouses denied benefits is small.
However, it is expected that the number will grow as more states consider granting gay couples the right to marry.