OTTAWA—The Supreme Court of Canada is set to rule Tuesday on a key part of the Conservative government’s tough-on-crime agenda.

The high court will deliver its ruling in a pair of cases involving mandatory minimum sentences for gun crimes.

The Ontario Court of Appeal struck down the law in 2013, calling it “cruel and unusual punishment,” so the province is appealing.

The Appeal Court struck down both the three-year mandatory minimum for a first offence of possessing a loaded prohibited gun, as well as the five-year sentence for a second offence.

The government is urging the Supreme Court to reverse that ruling, arguing the law does not breach the charter protection against cruel and unusual punishment.

The new sentencing rules were enacted in 2008 as part of a sweeping omnibus bill introduced by the federal Conservatives.