Well, in the U.S., I'd guess it would depend on what state you lived in. Actually, probably not, as long as it wasn't one of those trick canes with a blade inside.
What would really be important is how the cane was used. If you used the cane to defend yourself against an unarmed mugger who was considerably smaller than you, you'd probably be in trouble. However, if you were up against an armed assailant, or multiple unarmed assailants, things would be much easier for you in court.
Usually, you are not supposed to escalate the level of force in the attack. If someone attacks you barehanded (and they're not the second coming of Bruce Lee), then you can't whip out a knife and cut him to ribbons. Tying into this, courts also look at disparity of force when you're defending yourself. This really comes into effect in matters where deadly force was used. If someone slapped me and I snapped his neck, then I'd be in deep doo-doo.
It really all comes down to staying within the legal guidelines established in your area and applying common sense to that. When all else fails, ask a lawyer. Since you're in Canada, I have no idea how a cane would be percieved by the local law enforcement. Here, it probably wouldn't be a big deal, especially if you walked as if you were using it, rather than swinging it to and fro as you walked about.
Babbling again.
Cthulhu