The polygamist family at the center of Sister Wives, the TLC reality show, would like to move back to Utah - but not until they are sure they won't be prosecuted for their chosen lifestyle.

Kody Brown, his four wives, and their 16 children were forced to move to Nevada after the first season of their reality show aired, for fear of prosecution in Utah. The family was investigated after Sister Wives thrust them into the public eye, but no charges were filed.

The Browns have filed a federal lawsuit alleging that Utah's bigamy laws violate the First and 14h Amendments. They are not asking the court to publicly recognize their marriage as legal; they just want protection from prosecution on the grounds that their 'marriage' represents 'intimate conduct' that is protected from unconstitutional intrusions via a 2003 Supreme Court decision that banished laws against sodomy.

This is not about the Browns' attempt to get Utah to recognize polygamous marriage, but rather to ask the federal courts to tell them they cannot punish intimate conduct,  Melissa Murray, assistant professor of law at the UC Berkeley School of Law, told the Christian Science Monitor.

Mr. Brown is legally married to only one of his wives; the rest have been spiritually married in ceremonies unrecognized by the state. The lawsuit argues that the Sister Wives family should be excempt from prosecution because they have not sought or obtained multiple marriage licenses and therefore have not violated Utah's anti-bigamy law.

The term 'bigamy' refers to the act of entering into a marriage while legally married to another. 'Polygamy' is a more general term to describe a person cohabitating with multiple partners, who are not recognized as being married by law.  In the case of the Sister Wives family, Mr. Brown is a polygamist but not a bigamist.

Utah in particular has a fraught history with polygamy. The earliest Great Basin settlers were Mormons led by polygamist prophet Brigham Young, who took over the westward expedition after their first leader, Joseph Smith (who also reportedly had multiple wives), was executed by a mob. The Mormon faith places a high value on creating large familiies - believing that the larger your family, the greater your chances of reaching the highest level of heaven (or The Celestial Kingdom).

Taking multiple wives increases a man's chances of producing a great number of children. Also, many women lost their husbands during the westward expansion, and it was considered a duty among surviving men in the group to take them on as their own wives to spare the women the struggle of being a widow.

But by the late 19th century, after the Mormons had established a visible, functioning community in Utah, larger political concerns forced them to publicly abandon polygamy in order for Utah to be granted statehood. Although the concession was neccessary in order for Utah to be accepted into the union, the decision has had far-reaching consqequences for the state and for Mormons.

The official Mormon church - The Church of Jesus Christ of Latter-day Saints, or LDS - renounced polygamy at the time of the concession, and remains one of the practice's harshest critics. Those who believed that polygamy (or Celestial Marriage as it is known) should continue to be upheld formed splinter factions that preserved the beliefs and practices of the early Mormons.

LDS does not recognize any of these splinter factions as being Mormon. One of these factions is  the Fundamalist Latter-Day Saints (FLDS), famously led by Warren Jeffs; another is Apostolic United Brethren Church, of which the Browns are members.

We only wish to live our private lives according to our beliefs, Mr. Brown said in a statement made through his attorney to the New York Times.

Paul Murphy, spokesperson for the Utah Attorney General's office, told the Christian Science Monitor he did not expect the Browns to be successful, just as the last two cases that challenged the state's right to regulate marriage failed to make an impact.

There doesn't seem to be anything new here, Murphy said. This is just another challenge, and we expect the courts to uphold the over 100 years of tradition with family law.