Matt Volz, The Associated Press 12:07 p.m. EDT August 28, 2015

Nathan Collier with his wives, Christine and Victoria(Photo: Courtesy of Nathan Collier)

HELENA, Mont. — A Montana man is asking a federal judge to strike down the state's bigamy laws so he can marry a second wife.

Nathan Collier, his legal wife Victoria and his common-law wife Christine filed a lawsuit Thursday in U.S. District Court in Billings, Mont. They cite the U.S. Supreme Court's June ruling allowing gay marriage and reference biblical figures with multiple wives in their argument that the state is unconstitutionally preventing them from legitimizing their polygamous relationship.

Nathan Collier, 46, said he's fighting for marriage equality for polygamy.

"I'm fighting for my family's right to exist as a family," he said. "I can't imagine a greater cause to fight for."

He said he is a former Mormon who was excommunicated for polygamy and now has no religious affiliation. He and his family made their relationship public by appearing on the reality TV show Sister Wives in January.

Nathan and Victoria Collier, 40, married in 2000. He and his second wife, Christine, had a religious wedding ceremony in 2007 but did not sign a marriage license to avoid bigamy charges, he said.

Combined, the trio have eight children from their present and past relationships.

"My second wife, Christine, who I'm not legally married to, she's put up with my crap for a lot of years," Nathan Collier said. "She deserves legitimacy."

Montana, like all 50 states, outlaws bigamy — holding multiple marriage licenses. But the Supreme Court's chief justice, John Roberts, said in his dissent of the same-sex marriage ruling that people in polygamous relationships could make the same legal argument that not having the opportunity to marry disrespects and subordinates them.

After the Supreme Court's ruling in June, Yellowstone County officials denied Nathan and Christine Collier's request for a license.

State laws that forbid a man from marrying more than one woman denies them their constitutionally guaranteed rights to equal protection, due process, free speech, freedom of religion and freedom of association, the Colliers' lawsuit said.

Nathan Collier said he wants a judge to prevent the state from enforcing those laws against consenting men and women in "plural relationships."

The lawsuit was filed in U.S. District Court in Billings. It names Montana Attorney General Tim Fox, Gov. Steve Bullock, Yellowstone County Attorney Scott Twito and Yellowstone County District Court Clerk Kristie Lee Boelter as defendants.

All of the defendants declined to comment on the suit.

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