'Fraid not Saph. The lethal dose of Capsaicin is 47.2 mg/kg. Most states ban a concentration of higher than 10% in a can, and most of those must be less than 60g (2 oz) total ingredients. So that's approximately 6g of capsaicin per can. Average weight in our country is an embarrassing 86.6 kg, so lets lowball it and go for 75 kg. Someone would need 3540 mg of Capsaicin to die, so the maximum police grade can would contain about two lethal doses. You'd have to spray the entire can down their throat, and you could only actually spray two people, which is not the point of using it as a deterrence weapon.
Eh? What? If you sit (alone) on the train tracks and try to stop a swiftly moving train carrying nuclear fuel/waste, and the engineers can't stop in time, it would be ruled a suicide. They might get in trouble for negligence, at worst. They know well ahead of time if there is going to be a crowd of protesters blocking the trains, to prevent that kind of tragedy.@Kraco: Because even in a stateless society, sitting on train tracks and killing yourself, the people you were with, the train conductor who didn't see you, and anyone else by the consequences of your actions is considered something along the lines of murder.
I would not be surprised if there are other countries that don't care and just run them over, and probably have regulations in place to prevent that. I'm also willing to bet if you try that shit in the US, you'll get shot at. The NRC takes fuel and waste transport and the terrorist threat (or backyard atomic energy hobbyist threat) of obtaining any nuclear material very seriously.