Wardriving by itself is legal under Canadian laws... But it isn't to publish the information found when you wardrive (the dump, map, etc...) and to use without permission bandwidth of others. I do not know American law well, but common sense told that the same kind of laws applied, but sometime some American laws look strange for foreigner ;-) I do not see why it should be illegal… By doing so, the technology by itself will be illegal (wifi probe for network) ;-p