A senior Federal Court judge presiding over an unprecedented challenge of federal cabinet powers has scheduled a one-day hearing in January to begin hearing legal arguments over the Trudeau government’s sweeping prohibition of assault-style rifles.

The court session will address only two matters, but will settle whether the ban should be suspended temporarily while a wider court action against the unilateral measure continues.

The prohibition on May 1 instantly made certain firearms held by thousands of gun owners illegal, but the government has so far been unable to establish a compensation buy-back program to acquire the weapons through an amnesty period. The firearms, meanwhile, cannot be used.

Parliament was not involved, and no legislation, even for cost estimates, has been introduced. There’s been no similar legal event in the past four decades of incremental government changes to firearm law in Canada.

The January court sitting will also hear two objections, or challenges, to the government’s first expert-witness testimony: an affidavit sworn by the manager of a special RCMP branch that drew up the list of rifles and other weapons that were instantly banned.

The manager, forensic scientist Murray Smith, was head of the RCMP’s Specialized Firearms Support Services unit in the Canadian Firearms Program from 2008 to 2020, when he retired soon after the unit completed the new firearm prohibitions on May 1.

Smith’s affidavit pointedly questioned members of the firearm industry for their opinions of the effect the prohibition had on certain guns, bluntly suggesting they had made incorrect assumptions about technical aspects