Two former religious leaders in B.C. have been found guilty of polygamy after marrying more than two dozen women over the course of 25 years.

Winston Blackmore, 60, and James Oler, 53, were convicted of practising plural or "celestial" marriage in the fundamentalist community of Bountiful, B.C.

In B.C. Supreme Court on Monday, Justice Sheri Ann Donegan said Blackmore "subscribed to beliefs and practices of the Fundamentalist Church of Jesus Christ of Latter-Day Saints," a Mormon sect that believes in plural marriages.

James Oler, another former leader from the same community, was accused of having five wives and Blackmore 24 wives.

Both men are former bishops of the sect in the province's southeast. Neither denied having multiple marriages and Blackmore has fathered more than 145 children from his marriages.

"I'm guilty of living my religion and that's all I'm saying today because I've never denied that," Blackmore told reporters after the verdict.

"Twenty-seven years and tens of millions of dollars later, all we've proved is something we've never denied. I've never denied my faith. This is what we expected."

Maximum sentence is 5 years

The 12-day trial heard from one of Blackmore's ex-wives, Jane Blackmore. She told the court that Blackmore once told her he was "only doing what God told him to do."

In her ruling, Donegan said she found Jane Blackmore to be a "thoughtful, credible" witness. The judge also said Blackmore was "deliberate" in his marriages and "would not deny who he was or what he believes in" in interviews.

Blackmore's co-accused, James Oler, arrives at B.C. Supreme Court in Cranbrook on Monday. (Todd Korol/Reuters)

Blackmore's lawyer, Blair Suffredine, previously said he'd launch a constitutional challenge to the validity of the polygamy laws if his client were to be found guilty.

The trial also heard from mainstream Mormon experts and law enforcement officials who worked on the case. Up to 700 records seized as part of the investigation outlined the "celestial" marriage practice.

A celestial marriage is a secretive, plural marriage not registered with any higher governments — but records were kept in a vault in Texas.

Section 293 of the Criminal Code of Canada explicitly bans polygamy and threatens offenders with a five-year prison term.

Both Blackmore and Oler have been released on bail.

Trial decades in the making

The legal fight began in the early '90s when police first investigated allegations that residents of an isolated religious community were practising multiple marriages.

In 2014, Blackmore appeared outside the courthouse in Creston, B.C., with a number of his daughters, who came to support him. (CBC)

A lack of clarity around Canada's polygamy laws initially led to failed attempts at prosecuting Blackmore, followed by several efforts to clarify the legislation, including a reference question to the B.C. Supreme Court.

Oler was married to Blackmore's sister, and was chosen to lead the Canadian community just north of the U.S. state of Idaho following Blackmore's excommunication from the sect in 2002 by Warren Jeffs, considered the prophet and leader of the group.

Authorities have said Jeffs still leads the sect from a Texas prison, where he is serving a life sentence for sexually assaulting underage girls he considered brides.

The court ruled in 2011 that laws banning polygamy were constitutional and did not violate religious freedoms guaranteed in the Charter of Rights and Freedoms.

The mainstream Church of Jesus Christ of Latter-Day Saints, based in Utah, officially renounced polygamy in the late 1800s and disputes any connection to the fundamentalist group's form of Mormonism.

A sentencing date has not yet been set, but a hearing will be held next month in Kamloops to decide a timeline.