The one-year mandatory minimum jail sentences for accessing or possessing child pornography are unconstitutional, the Supreme Court of Canada ruled on Friday.

In a 5-4 decision, the top court said although the sentences contribute to the objectives of denunciation and deterrence, they also remove judges’ discretion to impose sentences other than imprisonment when appropriate.

Conservative politicians swiftly denounced the ruling.

In a social media post, Alberta Premier Danielle Smith called the judgment “outrageous” and urged the federal government to overturn it using the Constitution’s notwithstanding clause.

Conservative Leader Pierre Poilievre indicated his party, should it form government, would use the notwithstanding clause to overturn the “disgusting” ruling as well as reintroduce mandatory minimum sentences for possession of child sexual abuse material.

Conservative MP Larry Brock, the party’s justice critic, said the decision was a “cruel insult” to victims.

The decision affirmed a ruling of the Quebec Court of Appeal, which said the mandatory minimum sentences violated the Charter guarantee against cruel and unusual punishment. The Court of Appeal decision flowed from the cases of two men who pleaded guilty to child pornography offences.

The Crown and the attorney general of Quebec appealed to the Supreme Court, which heard the case in January.

A majority of the top court said a mandatory minimum sentence does not necessarily violate the Charter protection against cruel and unusual treatment or punishment.

However, when the application of a mandatory minimum sentence is broad and covers a wide range of circumstances, the sentence is constitutionally vulnerable because it leaves no choice but to impose a grossly disproportionate sentence on certain offenders, the court said.

In order to determine whether a mandatory minimum sentence complies with he Charter, a two-stage contextual and comparative analysis is required, Justice Mary Moreau wrote on the behalf of the majority.

The first stage involves determining a fit and proportionate sentence for the offender in question and possibly other reasonably foreseeable offenders, she said.

The second stage requires a comparison between the sentence that was determined at the first stage and the mandatory minimum sentence, including the extent of the disparity between these two sentences.

The use of “reasonably foreseeable scenarios” is indispensable to effective constitutional review, because the goal is to ensure it applies to all citizens, not just the person in a position to challenge the validity of a law, Moreau wrote.

In deciding the appeal, the Supreme Court examined a scenario in which an 18-year-old receives via cellphone, from his friend of the same age, an explicit photo of the friend’s 17-year-old girlfriend.

The recipient keeps the image on his cellphone and looks at the photo briefly, knowing that it constitutes child pornography.

In the age of digital communication, “it is not far-fetched” that an 18-year-old might receive from a friend an image corresponding to the definition of child pornography, Moreau wrote.

Although the actions of the representative offender in this scenario are serious and deserve to be denounced, they fall at the low end of the gravity scale for the crimes of accessing and possession of child pornography, she said.

“The offender’s youth and the fact that he received a photograph without requesting it and has no criminal record are significant mitigating circumstances,” Moreau wrote.

Imposing a sentence of one year’s imprisonment on the 18-year-old representative offender — when a fit punishment would be a conditional discharge with strict probationary terms — would constitute a grossly disproportionate sentence, she said.

The offence of possession of child pornography covers a very wide range of circumstances, Moreau said.

“Indeed, this crime captures both the well-organized offender who, over the years, has accumulated thousands of files, and the offender who, one day, keeps a file that was sent to the offender without them requesting it,” she wrote. “The mandatory minimum sentence must also be imposed regardless of the content of the child pornography.”

The experience of prison is likely to be particularly harmful to a young adult without promoting his awareness and rehabilitation, Moreau said.

Moreau noted the Supreme Court, in a previous ruling, said sentences imposed for sexual offences against children must correspond to Parliament’s legislative initiatives and the contemporary understanding of the profound harm that sexual violence against children causes.

The mandatory minimum sentences at the centre of the current case “go beyond what is necessary to attain their objectives,” Moreau wrote.

Parliament’s other initiatives and the state of the case law “ensure the imposition of severe sentences prioritizing denunciation and deterrence for crimes related to child pornography,” she added.

Moreau said while it can be assumed the mandatory minimum sentences in this case contribute to the prioritization of these objectives, “they also have the effect of removing judges’ discretion to impose sentences other than imprisonment in the appropriate circumstances.”

She suggested Parliament may wish to maintain minimum sentences for certain crimes while respecting the limits imposed by the Charter.

Moreau said while there is no single formula for doing so, Parliament could limit the scope of mandatory minimum sentences to certain conduct, or allow judges to exempt outliers for whom the mandatory minimum would amount to cruel and unusual punishment.