Canada's criminal prohibition of polygamy isn't designed to target religion, but the practice does seem to be most harmful when it is connected to a religious belief, a lawyer for the B.C. government said Wednesday during a landmark court case examining the law.

Opponents of the law, including a small religious sect in Bountiful, B.C., argue the ban infringes on their charter right to religious freedom.

Craig Jones said the province accepts that some people, including the self-described fundamentalist Mormons in Bountiful, practise polygamy because of deeply held religious views. But he said that doesn't mean they should be immune from the law.

"We've seen the extent to which religion is used as the control mechanism, as the enforcement mechanism that magnifies the harms of polygamy," Jones said during his third day of final submissions at the constitutional reference case being heard by the B.C. Supreme Court.

"The evidence that has emerged from expert and lay witnesses alike is that the greater the religious fervour with which polygamy is intertwined, the more harmful it can be expected to be. There is something significantly harmful about the religious manifestation of polygamy."

The court was asked to determine whether the law against polygamy is constitutional following the failed prosecution of two community leaders from Bountiful in 2009.

Residents of Bountiful are members of the Fundamentalist Church of Jesus Christ of Latter Day Saints, or FLDS, which, unlike the mainstream Mormon church, still encourages polygamy.

Religious practices not above law

Critics argue the law violates several sections of the Charter of Rights and Freedoms, most notably those dealing with religious freedom and discrimination. They also claim the law is too broad and targets innocent relationships involving more than two people.

The provincial and federal governments insist polygamy is inherently harmful, leading to physical and sexual abuse, teenage brides, human trafficking and other crimes. They also say polygamy affects the broader society, regardless of whether a particular polygamous marriage is good or bad.

Those harms, the governments say, outweigh any claim to religious freedom.

"Religiosity of a practice does not automatically render it immune from prosecution," said Jones.

"There are few crimes that have not, at one time or another, been excused on religious bases, from petty theft to genocide. Clearly, criminal activity such as female-genital mutilation, honour killings, ritual animal sacrifice and cannibalism may be deeply connected with cultural or religious beliefs."

And even without religion, Jones argued, polygamy is still harmful. In any society in which men marry multiple women, the pressures created by the reduced supply of potential wives will cause all of the same problems, he said.

Jones also rejected the argument that the law — rather than polygamy itself — is really what's harming the women and children of Bountiful.

Groups opposing the law have suggested criminalizing polygamy drives it underground, leading to the secretive isolation that has come to define the polygamous community in southeastern B.C. The law puts Bountiful residents under psychological stress, critics have argued, and makes it impossible for them to report crimes and seek outside help.

Prosecutors reluctant

"Decriminalizing polygamy is unlikely to make Bountiful less insular," said Jones.

"It seems fantastic to suggest that these crimes are hidden because polygamy has been driven underground. These crimes are hidden because they are crimes. They flow from polygamy and they need to be kept secret in order for their perpetrators to be able to continue committing them."

Bountiful has been subjected to several RCMP investigations during the past 20 years over allegations including polygamy, child sexual abuse and human trafficking, but prosecutors repeatedly declined to lay charges. That changed in early 2009, when a special prosecutor recommended polygamy charges against the community's two competing bishops, Winston Blackmore and James Oler.

Blackmore was accused of having 19 wives, but the constitutional case has heard he has as many as 25. Oler was accused of having three wives, but the court heard he now has five, allegedly including an American girl he married when she was 15.

A judge later threw out the charges because of how the provincial government chose a special prosecutor, prompting the government to order the ongoing constitutional hearings. The case is expected to eventually end up at the Supreme Court of Canada.