JACKSON -- Four lesbian couples are asking a federal judge to immediately stop Mississippi from enforcing a law that bans same-sex couples from adopting or taking children into foster care.

The request for a preliminary injunction was filed Friday in U.S. District Court in Jackson. The document said an injunction would only affect the four couples who are plaintiffs.

The couples and two gay-rights groups, the Campaign for Southern Equality and the Family Equality Council, filed suit Aug. 12 to challenge Mississippi's 2000 law that set the adoption ban.

It was not immediately clear how soon U.S. District Judge Daniel P. Jordan will consider the request filed Friday. A preliminary injunction would stop the state from enforcing a law while it is challenged in court. A judge can grant injunction if it appears that the people who filed a lawsuit would face irreparable harm by letting the law remain in place, and if they appear likely to win the suit based on their legal arguments.

The couples point out that Republican Gov. Phil Bryant said in his 2014 State of the State address that he wanted all children to be born into a "mature, two-parent family." They say allowing same-sex couples to adopt would help fulfill that goal.

Bryant, who is seeking re-election this year, has said many times that he opposes adoption by same-sex couples.

Mississippi is the last state to ban adoptions by same-sex couples. Lawmakers in Florida and Michigan reversed bans earlier this year, while courts in Louisiana and Nebraska struck down rules or laws in those states.

The court document filed Friday in Mississippi says plaintiffs Donna Phillips and Jan Smith, of Brandon, were married in 2013. The marriage took place out of state because Mississippi had banned same-sex marriage until a U.S. Supreme Court in late June wiped away such prohibitions nationwide.

Phillips and Smith have an 8-year-old daughter, but only Phillips is legally recognized as a parent of the girl, who is identified in Friday's court filing only by her initials, H.M.S.P. The document says Smith wants the same legal recognition through adoption.

"As Jan and Donna found out, the Mississippi Adoption Ban makes something as ordinarily simple as registering their child for public school an arduous process," the document says. "Because Jan is the legal owner of their home but is not recognized as H.M.S.P's legal parent, every year she is required to complete an agreement 'renting' her home to Donna and H.M.S.P. to prove that H.M.S.P. lives in the school district."

Plaintiffs also say the adoption ban interferes with the ability of both parents in a couple to fully participate in making education decisions and emergency medical decisions for their children.

Former Gov. Ronnie Musgrove, a Democrat, has said in recent years that he regrets signing the law that's now being challenged.