Eight gay and lesbian couples have filed a federal lawsuit in Nevada seeking equal marriage rights.

The couples are being represented by Lambda Legal and Education Fund. Sevcik v. Sandoval is the legal group's first marriage equality lawsuit filed in federal court, marking a strategic shift for Lambda Legal.

Two women in their seventies who have been together more than 4 decades are the lawsuit's lead plaintiffs. Republican Governor Brian Sandoval is the named defendant.

Beverly Sevcik, 73, and Mary Baranovich, 76, have raised three children and have four grandchildren.

Nevada lawmakers in 2009 overrode a veto from then-Governor Jim Gibbons to approve domestic partnerships, which provide gay couples some of the protections of marriage.

Lambda Legal staff attorney Tara Borelli told gay weekly Metro Weekly that the state's decision to create a parallel institution for gay couples is “irrational.”

“One of the reasons that we're suing in the state of Nevada is that this is a particular equal protection problem that this case examines. It's the kind off problem created where a state excludes same-sex couples from marriage, deems them fit for all the rights and responsibilities of marriage through a lesser second-class status – I this case, domestic partnership. That shows just how irrational that state's decision is to shut same-sex couples out of marriage,” Borelli said.

Previously, Lambda Legal had warned other groups against pursuing litigation in federal court, saying a loss in the U.S. Supreme Court would set back the marriage equality movement. The new suit then suggests that the legal group believes the high court would rule in its favor.