the new “must have” weapon of the Mexican drug gangs may be the P90
>>> Which [the P90], of course, is illegal for any US citizen to buy or possess. Only military and “law enforcement” may own them.
Where are you getting that? In certain states, maybe, but not by federal law. The feds will even OK your adding a full-auto happy button, as long as you jump through the paperwork hoops & pay the NFA fee.
I think that manufacturer’s pistol which uses the same ammo (whose model name I forget at the mo’) is no longer in production and likely banned from current import to the US, but not illegal to own.