0frollardBest Answer 9 years ago I'm from canada, and I have built 3 pneumatic cannons.You need to read the criminal code and find the sections on firearms -- then find the firearms act to find the definition of a firearm.As it turns out, potato guns fire OVER the threshold of kinetic energy of a firearm, but FAR under the velocity requirement - and since BOTH have to be met, then they are legal per the firearms act.THAT SAIDIn canada, ANYTHING that could be used as a weapon is a weapon under the eyes of the law if they so choose to see it that way. It's not illegal to walk down the street with a crowbar, but you'd better believe you'll be hassled for looking dubious.Back on topic - I've spoken to MANY mountie/bylaw officers/city police (I work for 911) -- and none of them would outright charge you for having one. If you were walking down the street with it, they'd take it away but no charges. Best bet is to find a friend with a ranch or go out of town to somewhere the property owner doesn't mind you going all newtonian on him. IF YOU FIRE ANY PROJECTILE AT ANY SPEED AT ANY PERSON IT IS ASSAULT WITH A WEAPON AND YOU WILL GO DOWN HARDER THAN YOU CAN IMAGINE. Play safe.