I had someting happen when entering back into Canada the other weekend. The border agent specifically asked if we had 'self defence' weapons, and my wife piped up that I had a pocket knife. Fuck. It turns out that any knife you can open with one hand (ex: thumb stud) is now illegal to cross the border with. The agent even explained that yes, I can buy the knife at Canadian Tire/Walmart/etc in Canada, but the moment I cross the border with it (ex: to the US and then back into Canada again), there is now an issue. He was cool about it, explained what is what now, and told me to leave the knife home next time. I'll have to take my old school pocket knives next time (the ones you need to use two hands to open).