The way the "law" was written, if the gun can possibly produce or has the potential to produce over 10,000 joules, it is prohibited - as well as any firearm with a bore larger than 20 mm. So, 8 bore or larger are automatically prohibited as dangerous firearms.
Those of the black powder community are in confusion as to if their muzzleloading cannon are included in this "new" size classification.

"The verbiage is VERY important and was done with careful consideration" - that statement by the Federal Minister guilty of these changes to the code.