Should we look toward the Law of the Sea and anti-pirate laws to regulate Private Military Companies? The use of military force is based on international norms and agreements. Through either tacit or implicit permission of organizations and states, an actor, generally a state can use its military. Of course, it used to have freedom to wield its Weberian monopoly of legitimate force within its borders at its leisure, but times have changed.
The latest wave of globalization has reversed border ossification of the last 150 years to allow penetration of domestic policies. With mixed results, states have influenced internal politics of states (Tianamen, Cote d'Ivorie, Congo, FYR, PNG, Sri Leone, etc) to make their constituents 'feel' better about the world in which they trade and conduct commerce and communication because much of the time these external regions really had little, if any, direct impact on the outsiders. Today, however, we have military forces outside the direct control of the state and possibly outside the Weberian-defined norms.
The effect of these PMCs have to influence states and peoples, possibly outside the control of states, must be regulated. States and corporations do not not uncertainty by their nature, at least those who operate in the institutionalized with our Disneylands, 401(k), and minimal need for personal protective services.
Mercenary companies were once outlawed as interfering with state business. The Laws of the Seas, with its international cooperative construct that does not require ascension like the WTO, be a fair model for a global agreement on military force? The multi-lateral agreement between all states bordering the seas is functional, should it be extended? What about the growing piracy menace? Is it cover for 4GW 'warriors', terrorists, or something else?