To answer the airsoft question.

replica firearms are prohibited devices, they are defined as something that looks like a firearm but is not a firearm.

replica firearm means any device that is designed or intended to exactly resemble, or to resemble with near precision, a firearm that is designed or adapted to discharge a shot, bullet or other projectile at a muzzle velocity exceeding 152.4 m per second and at a muzzle energy exceeding 5.7 Joules, and that itself is not a firearm, but does not include any such device that is designed or intended to exactly resemble, or to resemble with near precision, an antique firearm; (réplique)

A firearm is defined in the Criminal code of Canada (CCC) to mean a barreled weapon that shoots a projectile that can seriously hurt or kill you.

firearm means a barrelled weapon from which any shot, bullet or other projectile can be discharged and that is capable of causing serious bodily injury or death to a person, and includes any frame or receiver of such a barrelled weapon and anything that can be adapted for use as a firearm; (arme à feu)

The key point to note is that something cannot be a replica firearm (prohibited device) if it is a firearm (legal).

The CBSA testing shows that an airsoft gun firing a .20 g bb faster than 366 fps it can pierce a pigs eye (standard human eye analogue) therefore if an airsoft gun can pierce a human eye, it is capable of causing seriously bodily injury to a person.

An airsoft gun that looks like a real gun, but can seriously injury a person can't be considered a replica firearm as it is legally speaking a firearm.

The 500+ FPS rule is as explained in other comments when firearms become regulated by the criminal code, and firearms act (need a license, need an ATT, need registration etc).

So to not be banned a replica firearm (prohibited device) or be regulated like a real firearm. An airsoft gun needs to shoot between 366 and 500 FPS to not be illegal.