Military and hollowpoint ammo...

[spartacus2002]

Explosive projectiles are prohibited if they are used directly against personnel. However, if they are used against fortifications, or used with intent to kill through fragments or shrapnel, they are perfectly legal. In other words, if you are charged by the Mongol hordes and you have a 20mm Orlikon, you cannot shoot directly at them. You can shoot at the ground and kill them with fragments.

Urban Legend. All DoD weapons systems are vetted against the Hague conventions and other customary international law, and are approved for use against personnel. There may be local Rules of Engagement prohibiting certain items like tear gas, or like tying rope between the tripstakes on anti-tank mines, but you can use .50cal MGs on the enemy.