[Debrief]

Airsoft guns are devices that have a low muzzle velocity and muzzle energy, and usually discharge projectiles made out of a substance such as plastic or wax rather than metal. An airsoft gun, firing a .20g 6mm plastic pellet, with a muzzle velocity below 111.6 m/s (366 fps), and resembling with near precision an existing make and model of a firearm, other than an antique firearm, is a replica firearm and therefore a prohibited device.

Replica firearms are prohibited devices in Canada.

From the Criminal Code:

“prohibited device” means

(e) a replica firearm;

I don't see what there is left to argue about.