TULSA, Okla. (AP) – Four women have filed a federal lawsuit challenging a constitutional amendment passed by voters that bans same-sex marriage.

The women filed a civil rights lawsuit in U.S. District Court in Tulsa that seeks to do away with the state constitutional amendment that defines marriage as a union between a man and a woman.

The ban also prohibits giving the benefits of marriage to unmarried couples in Oklahoma. Same-sex marriages in Oklahoma are not recognized.

Broken Arrow residents Mary Bishop and Sharon Baldwin and Tulsans Susan G. Barton and Gay E. Phillips filed the lawsuit.

Kay Bridger-Riley, an attorney for the plaintiffs, said she was proud to represent what she called “their really important lawsuit.”

In addition to seeking to overturn the state constitutional amendment, the case challenges the constitutionality of the federal Defense of Marriage Act, which permits states to ignore same-sex weddings performed in other states.

Voters in 10 other states approved bans on same-sex marriage in the Nov. 2 elections.

Bishop and Baldwin have been living in a committed relationship for eight years, while Barton and Phillips were joined in a civil union conducted in the state of Vermont in 2001, according to the suit.

The lawsuit claims the women have been denied the rights and privileges of other citizens within the state of Oklahoma and the United States of America.

The state constitutional amendment and DOMA violate the plaintiffs’ right to either enter into a marriage contract or have their civil union recognized by the state of Oklahoma, according to the lawsuit.

Bishop is an assistant city editor of the Tulsa World, and Baldwin is a copy editor for the newspaper.

Baldwin and Bishop said they had a commitment ceremony four and a half years ago and have spent nearly $1,300 on legal arrangements to make them as legal “in the eyes of the law” as a married, heterosexual couple.

“We still do not have the same rights and privileges and legal responsibilities that married couples have, and we want to have the rights and the responsibilities,” Bishop said.

“And we want the recognition of our union,” Baldwin said.