A federal judge has ruled that a law banning polygamy in the state of Utah is unconstitutional.

US District Judge Clark Waddoups ruled in favour of the Brown family, effectively decriminalising polygamy in the state.

The family’s lawsuit, filed in 2011, relied heavily on a 2003 ruling in Texas to decriminalise sodomy, which at the time was celebrated by gay rights advocates.

The original stance from the Utah Attorney General, Mark Shurtleff, was that the two laws were not comparable, because the polygamy law involves whole families, rather than just two consenting adults.

Nonetheless, Judge Waddoups handed down a 91-page ruling in favour of the Brown family on Friday.

It said that, while there was no “fundamental right” to practice polygamy, the Utah’s state law making cohabitation, in particular the phrase: “or cohabits with another person”, violated the first and 14th amendment rights.

He said the law was outdated, and referred to the 1800s when cohabiting held more legal weight than today.

During the trial, the judge concentrated heavily on what defined a polygamous relationship, and the differences between a polygamous marriage, and an unmarried man having relationships with several women.

The Brown family found some fame in appearing on the TLC television programme ‘Sister Wives’.