I didn’t know that. What is the difference between this, and “built-in” shrapnel in explosives (from a legal perspective)? The end result is all the same after the explosion
Only think I know is that fragment size can't be too small, maybe you can argue that a nail is untested and thus can make micro fragments? Curious to know why this wouldn't be allowed
Edit: looks like there is a general ban on "unnecessary suffering or superfluous wounds", so if the nails are strong enough to injure but not kill, they are prohibited.
I'd imagine a thin 3d printed jacket filled with ball bearings will exponentially increase the amount of shrapnell, it this ghetto variant looks nasty too.