Maybe if I was 16 years old and had nothing to lose I would be glad to cover my car in leaf stickers but I live in the real world. I wouldn't do anything to give a law enforcement official heads-up about my smoking habits. Having these stickers isn't illegal and I HIGHLY doubt I would be pulled over simply for having one of these on my car. Though, what happens when I am out at 2am and one of my headlights goes out resulting in me getting pulled over? If that cop happens to notice one of my pro-canna stickers do you think he is more or less likely to ask to search my car?

They call it "bumper-sticker-activism" for a reason. It's really nothing more than an attempt to piss off whoever is tailgating you and to me that isn't worth getting busted over.