It depends. Different militrary groups might see the geneva convention rules a bit differently. The is a section that refers to rounds that cause undue suffering are not alowed and a few years ago we were told a 50BMG on a person was a no no....you could you use to take out equipment though (radio, weapons, helmets) not your fault if they are wearing it :wink:
Recently a friend was just deployed and none of this was dicussed during his ROE briefing.
Often what is on paper and what happens in reality are two seperate things. You don't mount a '50 on a hummer and hope you dont run into infantry cause you aint allowed to plow though them. You light'em up.
The only suffering they get is the last electron going off in thier spinal cord. You rarely live after getting hit with a .50, the shock alone is a killer, even if it hits your leg.
I was never informed of this rule by a superior, I was actually told this by a buddy. Not that it mattered to me, I wasn't issued a M82. I don't even know if its true or not.
I actually sawa picture in the paper of an Army SF sniper with a M82, caption read "American Special forces uses large caliber rifle to kill the enemy at extreme distances."