With 17 of their 25 children still living at home, breakfast is a military operation for the Dargers.

As organized chaos unfolds at the family home in the Utah countryside outside Salt Lake City, the parents come to help out.

Alina is the first, followed by her "sister wives" Vicki and Valerie, and finally their husband Joe.

The Dargers are members of a polygamous marriage, a lifestyle they say is endorsed by their fundamentalist Mormon beliefs.

Joe married cousins Alina and Vicki in 1990. Ten years later, Vicki's twin sister Valerie joined them, after her first plural marriage broke down. She brought five children with her from that relationship.

The family has lived openly for several years now, even publishing a 2011 book entitled "Love Times Three".

But for a long time, Joe Darger says he worried that he might be arrested under the anti-polygamy laws in effect in the western US state.

"The fear when I went public four years ago, that fear was very real," he told AFP.

"This is a third degree felony... this is serious prison time. My grandfathers were imprisoned, so that was a real impact that we felt."

That fear has lifted for now, following a December ruling by a federal judge that struck down a key part of the state's anti-polygamy law as unconstitutional.

Judge Clark Waddoups ruled that legislation banning "unlawful cohabitation" was at odds with the constitutional right to freedom of religion.

Alina Darger, who herself works as a lawyer on cases involving polygamy, says the ruling was a relief.

"That's been one of the great things about the ruling -- the decriminalization, and the judge saying basically that the state needs to stay out of people’s bedrooms," she said.

"As long as it's adults freely choosing what they want, then I don't feel it would be my place to tell somebody else you can't choose to love who you love."

But what the Dargers see as unwarranted government intrusion, others see as essential for the protection of women and children.

Marion Munn moved to Utah from Britain after converting to a fundamentalist Mormon faith, and says she was part of a polygamous relationship for 18 years.

"The only way that I can explain it is like living with adultery on a daily basis, and having the woman come home," Munn said.

"On top of that you have to smile and pretend that everything's okay because that's part of the culture too."

She now argues that such marriages are inherently unequal, and often aren't entered into freely.

"Certainly within Mormon-based polygamy, it's not really much of a choice, because Mormon scriptures teach a woman that if she doesn't consent to living in polygamy, God's going to destroy her," Munn explained.

"So for me going into it, I didn't personally want to live it, but I felt compelled to as a matter of faith."

While the practice may work for the Dargers, a 2011 University of British Columbia study found polygamy causes greater levels of crime, violence, poverty and gender inequality in communities that practice it.

The United Nations has called for a ban, while polygamy has been at the center of notorious cases such as that of Warren Jeffs, the fundamentalist Mormon leader sentenced to life in prison for child sexual assault in 2011.

The main branch of the Mormon faith -- the Church of Jesus Christ of Latter Day Saints -- renounced the practice of polygamy in the 1890s under pressure from the US government.

While some offshoots of the religion continue the practice, exact numbers are hard to come by. Some estimates say that around 40,000 Utah residents live in plural marriages.

Utah's Attorney General Sean Reyes has yet to say whether he will challenge the federal court ruling on polygamy.

The state is also currently fighting to enforce a ban on gay marriage, which was ruled illegal in December by another federal judge.