yes mercenaries are real, they are often employed in 3rd world countries. some are well trained (such as executive outcomes in the early 90s), but the vast majority have no training and are just cannon fodder that are hired by whatever drug lord in africa or what not. no they are not legal according to the UN mercenary convention
and for the idiots claiming that blackwater and other contractor companies hired by the state dept are mercenaries- no, they are not. to quote the UN's definition of a mercenary (speaking of which, it is funny that someone even mentioned the UN mercenary convention without having the brains to actually read it)
1. A mercenary is any person who:
(a) Is specially recruited locally or abroad in order to fight in an armed conflict;
(b) Is motivated to take part in the hostilities essentially by the desire for private gain and, in fact, is promised, by or on behalf of a party to the conflict, material compensation substantially in excess of that promised or paid to combatants of similar rank and functions in the armed forces of that party;
(c) Is neither a national of a party to the conflict nor a resident of territory controlled by a party to the conflict;
(d) Is not a member of the armed forces of a party to the conflict; and
(e) Has not been sent by a State which is not a party to the conflict on official duty as a member of its armed forces.
2. A mercenary is also any person who, in any other situation:
(a) Is specially recruited locally or abroad for the purpose of participating in a concerted act of violence aimed at:
(i) Overthrowing a Government or otherwise undermining the constitutional order of a State; or
(ii) Undermining the territorial integrity of a State;
(b) Is motivated to take part therein essentially by the desire for significant private gain and is prompted by the promise or payment of material compensation;
(c) Is neither a national nor a resident of the State against which such an act is directed;
(d) Has not been sent by a State on official duty; and
(e) Is not a member of the armed forces of the State on whose territory the act is undertaken
blackwater and other PMCs involved in iraq and afghan do not fit into the first category because
-they are nationals and residents of a state in the conflict
-they are not hired to participate in hostilities. they are hired to provide security.
they do not fit in the 2nd category because
-they do not conduct activities described by section a
-they have been sent by a state on official duty