No spray, no airgun, no folding mace, absolutely nothing can be used in self defense.
Except for the alarm.
In the wake of the Kyle Rittenhouse stuff I remember Americans saying that going armed to a protest (not just that guy but others) was reasonable and routine because you might need to defend yourself if things go bad. In much of the rest of the west the general idea is that if you’re going somewhere you think you might need a weapon - you probably shouldn’t go.
But that's the point - if the courts have found that defense is lawful, then it becomes a question of why it's possession (not even use and proportionality) would not be. Then you end up in a weird state where people can make up reasons to have a hammer or something else on them rather than have something potentially more reasonable/effective like pepper spray. Allowing some limited non-lethal tool seems reasonable if defense is actually something to support.
Is there some research on this? Not just talking about guns, but even things like pepper spray.
"if you’re going somewhere you think you might need a weapon - you probably shouldn’t go."
I generally agree with this. I do wonder how this fits in the overall system. This assumes there are places that you could need a weapon, or where weapons could be used against you. It also assumes you always have a choice to avoid the area. If these high risk areas exist, how does the entire population avoid them? If that were even possible, the threats would also redistribute. Examples like Rittenhouse might be textbook for easily avoidable situations that turned bad (hence the news coverage), but I'm not sure it's representative of the full range of situations (the stuff that doesn't make the news).