Just five weeks after Pentagon lifted its Don't Ask, Don't Tell policy, a group of gay U.S. service members have filed a lawsuit challenging the constitutionality of the federal Defense of Marriage Act.

According to a report in the Boston Globe, the lawsuit asks the military to provide the same benefits to same-sex spouses as given to straight married military personnel.

DOMA defines a spouse as a member only of the opposite sex, and hence it prevents the military from providing same-sex couples with equal benefits.

This case is about one thing, plain and simple, Aubrey Sarvis, executive director of the Servicemembers Legal Defense Network, said in a statement reported by the Global Post. It's about justice for gay and lesbian service members and their families in our armed forces rendering the same military service, making the same sacrifices, and taking the same risks to keep our nation secure at home and abroad.

The lawsuit lists various benefits given to straight married couples which, the paintiffs claim, are wrongly denied to gays, including medical and dental benefits, housing allowances, travel and transportation allowances, survivor benefits and the right to be buried together in military cemeteries, reports the Associated Press.

Pentagon's Don't Ask Don't Tell policy barred gay people from serving openly in the military.

The main plaintiff in this case is Massachusetts Army National Guard Maj. Shannon McLaughlin, 41. She and her wife Casey, 34, have twins. If Shannon were to be deployed, Casey, who is a history teacher in a school, would no longer be able to take their children for regular medical appointments at a nearby military base, reports the Washington Post.

Under DOMA, the military is creating a second-class service member, Shannon McLaughlin told the Washington Post. It's amazing to me how many other similarly situated families there are out there.

Pentagon spokeswoman Eileen Lainez said Wednesday that officials were engaged in a careful and deliberate review of whether some benefits could be extended to same-sex partners.

Service members continue to have some benefits for which they may designate beneficiaries, regardless of sexual orientation, Lainez said in an email. But eligibility for other benefits is restricted by DOMA, she said, according to the report.