One of the major defining factors is whether they are held to the standards of military law within that country. For example the French Foreign Legion is part of the army and subject to French Military Court Martial. Whereas Triple Canopy in the US is a PMC(mercenary) due to the inability to Court Martial their “soldiers” for crimes in theater. They are only liable in the civilian courts which effectively means they are liable to no one.
One of the major defining factors is whether they are held to the standards of military law within that country. For example the French Foreign Legion is part of the army and subject to French Military Court Martial. Whereas Triple Canopy in the US is a PMC(mercenary) due to the inability to Court Martial their “soldiers” for crimes in theater. They are only liable in the civilian courts which effectively means they are liable to no one.