I don't think it's that simple. For starters, there's probably a very short list of people who own tacocopters, let alone people who own grenades. If it becom

I don't think it's that simple. For starters, there's probably a very short list of people who own tacocopters, let alone people who own grenades. If it becomes a problem, I can think of countermeasures -- register the things, ban them in public spaces/require flight plans, detect and triangulate the control signal. Heck, you could just look around; with a low tech system like that, whoever's flying the thing needs line of sight to it in order to identify the target. It's noisy and slow and I'd expect not nearly as effective as stealing a car and doing a drive-by shooting. But more than that, I'd be very surprised if that sort of thing becomes a problem. Normal people aren't murderers. Think about all the poisons, explosives, and highly kinetic pieces of equipment normal people have access to right now.