Actually, you can cross the border with them, I did. You simply tell them what you have, they'll write out an invoice and you go inside and pay the duty on it. The agent told me that as long as there isn't a law against them, and they are less than 500fps, they won't sieze them. Right now, everyone in Canada has to be 18 to buy any gun, bb, pellet, airsoft, and paintball.
On the seventh day when God rested, we overran his perimeter and we've been running the show ever since....