Prime Minister Justin Trudeau has ordered a major overhaul of Canada's criminal justice system that will put a new focus on restorative justice and hatch a priority plan to regulate and legalize pot.

Trudeau delivered mandate letters to each of his cabinet ministers Friday, and among the long list of priorities is a sweeping review of the last decade of laws and sentencing reforms brought in by the Conservatives.

"You should conduct a review of the changes in our criminal justice system and sentencing reforms over the past decade with a mandate to assess the changes, ensure that we are increasing the safety of our communities, getting value for money, addressing gaps and ensuring that current provisions are aligned with the objectives of the criminal justice system," reads Trudeau's letter to Justice Minister Jody Wilson-Raybould.

Under former prime minister Stephen Harper, the Conservatives took a "tough on crime" approach that increased prison sentences, toughened up the parole and pardon processes, and gave victims more say in the justice system.

Persistent overcrowding in prisons

During that time, there have been reports about overcrowding and the use of segregation in prisons, a disproportionately high number of aboriginals behind bars, and the inadequate treatment of mental illness.

The justice minister has been instructed to take on these issues as well.

The Liberal government will study Canada's penal policies to address problems of mental illness, indigenous offenders and the use of segregation in prisons. (Shutterstock)

"Outcomes of this process should include increased use of restorative justice processes and other initiatives to reduce the rate of incarceration amongst indigenous Canadians, and implementation of recommendations from the inquest into the death of Ashley Smith regarding the restriction of the use of solitary confinement and the treatment of those with mental illness," Trudeau wrote in his mandate letter.

Wilson-Raybould is also tasked with reviewing a series of constitutional challenges to Conservative laws that are now before the courts and make quick decisions on which appeals to drop.

Overall, the changes mark a fundamental shift to a less "punitive" approach to criminal justice, says Carissima Mathen, a law professor at the University of Ottawa.

"Prime Minister Trudeau has given Jody Wilson-Raybould a very full plate, a very ambitious agenda, a very challenging agenda, but one that if fully realized could really change the face of the justice system in Canada," she said. "So a potentially very exciting set of challenges."

Canada's Correctional Investigator Howard Sapers said many of the criminal justice reforms brought in over the last decade were ad hoc and ineffective.

'Rapid-fire' reforms

"They were rapid-fire reforms and often came without a lot of in-depth study and certainly without a lot of understanding about how all of these reforms would affect one another," he said. "The cumulative impact of this very rapid pace of change has yet to be fully felt so it's very important to stand back and have a look and to see whether there are some things that need to be re-calibrated, some things that need to be abandoned and other things that need to be accelerated and really try to re-introduce some coherence back into the system."

John Muise, a former Toronto police officer, National Parole Board member and victims' advocate, hopes the Liberal government doesn't roll back some of the sound measures the Tories brought in to improve public safety, such as tougher penalties for gun crimes and limits on accelerated parole for serious drug dealers.

"There were a number of mandatory minimum sentences and other things that were done that were thoughtful, that were evidence-based, that they just shouldn't touch," he said.

Along with Public Safety Minister Ralph Goodale and Health Minister Jane Philpott, Wilson-Raybould will also create a federal-provincial-territorial process that will lead to the legalization and regulation of marijuana.

One of Goodale's first priorities is to repeal the "problematic elements" of the controversial Conservative anti-terror law, known as C-51, in a bid to strike a better balance between security and civil liberties. He will also be in charge of creating a new office for community outreach and co-ordination for counter-radicalization.

Among the other priorities for the justice minister:

Lead a process, supported by the health minister, to work with provinces and territories to respond to the Supreme Court of Canada decision on physician-assisted death.

Address gaps in services to aboriginal people and those with mental illness throughout the criminal justice system.

Other priorities for the public safety minister: