An Ontario judge has struck down a two-year mandatory minimum sentence for drug traffickers, calling the penalty a form of "cruel and unusual punishment" for Indigenous offenders caught up in a "tragic history" within the criminal-justice system.

The decision is the third since last February to declare a mandatory minimum unconstitutional in the case of an Indigenous offender and it comes barely a week after Prime Minister Justin Trudeau and Justice Minister Jody Wilson-Raybould told aboriginal peoples that Canada "can do better" in criminal justice. Their comments followed a jury acquittal of Gerald Stanley, a white farmer, in the shooting death of Colten Boushie, a 22-year-old Cree man, in Saskatchewan.

The latest case centres on Cheyenne Sharma, a 22-year-old single mother, who pleaded guilty two years ago to bringing $128,000 worth of cocaine into Canada. Her grandmother went to residential schools and her mother spent some time in foster care. She ran away from home at 13 and, at 15, became a sex worker. She said she was paid $20,000 and accepted the assignment because she was behind in her rent and facing eviction. She was a 20-year-old mother of a two-year-old when she committed the offence. Justice Casey Hill of the Ontario Superior Court in Brampton said that while these circumstances do not provide an excuse for committing a serious crime, they do set out a context for deciding Ms. Sharma's degree of responsibility and what an appropriate sentence should be.

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Canadians aware of the "unique history of aboriginal peoples," he wrote in his 98-page judgment on Tuesday, would "conclude that such a sentence would outrage standards of decency." He said that she has taken steps, such as resuming her education, to rehabilitate herself and he sentenced Ms. Sharma to 17 months in prison."The courts are not isolated from the ongoing process of reconciliation and meaningful nation-to-nation dialogue involving Canada's aboriginal peoples," he wrote.

The ruling is part of a trend in which judges, citing the effects of minimums on Indigenous offenders, rule the punishments unconstitutional. Last February, the Northwest Territories Supreme Court did so in a case involving a firearms offence and, last July, the B.C. Court of Appeal did the same in a case involving a sexual offence.

Ms. Wilson-Raybould declined, in an e-mail to The Globe and Mail, to say when the government would act to keep her promise to eliminate some mandatory minimums.

"The Prime Minister has asked me to conduct a broad review of the changes in our criminal justice system and sentencing reforms over the past decade, and the examination of mandatory minimum penalties is included in this review. That work is ongoing," she said.

Jonathan Rudin, program director of Aboriginal Legal Services of Toronto, which intervened in the case, said he worries that the review means a long wait.

"Every day it waits, people go to jail who shouldn't go to jail," he said in an interview. "That should be keeping the Prime Minister and Minister of Justice up at night."

Mr. Trudeau had said in his mandate letter to Ms. Wilson-Raybould that she should seek "to reduce the rate of incarceration amongst Indigenous Canadians." Ms. Wilson-Raybould has promised on multiple occasions to scrap some mandatory minimums.

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The Public Prosecution Service, which operates independently from the Justice Minister, said it has 30 days to decide whether to appeal the drug-trafficking ruling, and declined further comment.

Federal prosecutors had sought a sentence of 3 1/2 years, citing Ms. Sharma's Indigenous background and saying it was well below the six to eight years that was standard for the amount of drugs she transported. But after Ms. Sharma's lawyer, Robert Christie, brought a constitutional challenge, prosecutors said her case was "extraordinary" and they would use their discretion to ask for a sentence of 18 months.

"The fact that the Crown thinks it's exceptional speaks to the fact that they don't really understand the circumstances of Indigenous people," Mr. Rudin said.

Mr. Christie had also asked Justice Hill to strike down Conservative-era limits on house arrest for drug traffickers, but the judge declined to do so.

Federal sentencing law passed by the Liberals in 1996 contains a clause telling judges to give particular attention to the circumstances of Indigenous offenders. The Supreme Court has interpreted that clause to mean a new way of looking at sentencing is needed in such cases.

Justice Hill said the Supreme Court and Truth and Reconciliation Commission, which looked at the history of Canada's forced residential-schools experience, recognized the state's contribution to "cultural genocide, the intergenerational effects of colonialism … and a 'tragic history' of the treatment of aboriginal peoples within the Canadian criminal justice system including the 'peculiarly devastating' impact of overincarceration."

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He cited statistics showing that Indigenous Canadians made up 27 per cent of prisoners in federal custody in 2016-17, and 26 per cent in provincial custody, but just 5 per cent of the overall population.

The decision was a kind of reprise of a case from 2004, in which Justice Hill sentenced three black, female drug couriers to house arrest. The Ontario Court of Appeal said jail terms should have been imposed, adding that a sentencing proceeding was "not the forum in which to right perceived societal wrongs."