The case of two Ontario human traffickers who are challenging their prison sentence as cruel and unusual punishment is again highlighting the ongoing problem with mandatory minimum penalties, legal experts say.

The two Kitchener, Ont., men pleaded guilty to selling the services of teenage girls for sex in Ontario motel rooms, but they are challenging the mandatory four-year minimum prison sentence as cruel and unusual punishment, documents obtained by CBC News show.

Minas Abara, 20, and Nicholas Kulafofski, 19, both from Kitchener, pleaded guilty to human trafficking and profiting from the sale of sexual services in June. They'd been involved in selling the sexual services of two girls, ages 14 and 17, in hotel rooms in Windsor, Ont. and London, Ont. in June 2017.

Abara and Kulafofski's lawyers are arguing the mandatory minimum sentence set out in the Criminal Code of Canada violates the men's right to be free of cruel and unusual treatment or punishment, a right in the Canadian Charter of Rights and Freedoms.

Mandatory minimum sentences have been part of the Canadian criminal code for decades for crimes such as murder, but many more were added under the Conservative government from 2005 to 2016.

Former Prime Minister Stephen Harper brought in mandatory minimum sentences as part of his tough-on-crime agenda, saying at the time there are certain crimes which must always require a prison sentence.

Canadian judges have previously struck down the mandatory minimum penalty for human trafficking but the sentence remains on the books. Legal experts expected the Liberal government would give judges more discretion in sentencing.

That could have happened with Bill C-75, an omnibus bill that amends parts of the Criminal Code and Youth Criminal Justice Act. But it doesn't touch mandatory minimums — a missed opportunity, said University of Toronto law professor Kent Roach.

"All you'd need is a simple provision that would say, judges can depart from any mandatory minimum," he said.

'A loss of freedom'

In the London, Ont., case, defence lawyers have filed their arguments against the mandatory minimum sentences. The Crown has until the end of September to file her arguments for sentencing. Justice Kevin McHugh will hear the lawyers' and Crown's arguments in October.

"A penitentiary term of four years would have an irreparable effect on (Abara). The loss of freedom, and separation from family and society at such a young age would be a trauma that (Abara) may never recover from," Abara's lawyer, Chris Uwagboe, wrote in a submission challenging the four-year penalty.

"It is likely that such a sentence would reinforce criminality rather than reform or rehabilitate from criminality."

Kulafofski's lawyer, Frances Brennan, suggests the judge impose a sentence of 15 to 18 months in jail and two years probation for her client.

Neither man used violence to keep the teens in the hotel rooms, their lawyers argue, though they did keep most of the money the girls earned.

The Liberal government is aware that "mandatory minimum penalties present serious challenges from a constitutional perspective," Celia Canon, a spokesperson for the minister of justice, wrote in a statement.

A third co-accused in the sex trafficking case, Paywand Sohrabzadeh, pleaded guilty to human trafficking as well as making child pornography and profiting from the sale of sexual services. He was sentenced to four years in prison. His lawyer is not challenging the sentence.

Mandatory minimums often challenged

This isn't the first time the mandatory minimum sentence for human trafficking has been challenged. In several previous cases, the mandatory minimum has been overturned by a judge as cruel and unusual punishment.

That's because mandatory minimums don't take into account individual circumstances of a crime, said Abby Deshman, the director of the criminal justice program at the Canadian Civil Liberties Association.

"We don't think that mandatory minimum sentences are a useful criminal justice policy. They disproportionately punish people who are low level offenders," she said.

Abara recently became a father and "being a father is his greatest joy and his self-professed greatest accomplishment," but the strict bail conditions under which he's living prevent him from earning a living and contributing to his household, his lawyer wrote in his submission to the judge.

Kulafofski is a first-time offender, his lawyer said.

Although proponents say mandatory minimum penalties are a way to be tough on crime, they don't deter criminals, Deshman said.

Judges need sentencing discretion

Forcing courts across the country to challenge mandatory minimum sentences one-by-one is unnecessary, Roach, the University of Toronto law professor and an expert on Canada's constitution.

"It should be up to a judge whether a sentence of four years would be appropriate or not, but because the government has left mandatory minimums there, they're being challenged province by province, court by court," Roach said.

Sentencing reform must stand the test of time, said Canon from the justice minister's office.

"Judges certainly should be provided the necessary discretion to impose sentences appropriate to the offender in front of them," Canon wrote. "Mandatory minimum penalties are being litigated quite extensively.… Our government is committed to ensuring that our criminal justice system keeps communities safe, protects victims, and holds offenders to account."

There have been no victim impact statements. Both men admitted to driving the victims to hotel rooms in London and Windsor. They posted pictures of the victims on an online site used by sex workers and communicated with men to set up meetings.