Nothing. Warlords exist when the current government is too ineffective to deal with them. See Afghanistan. A look into Greek history shows us that every time governments became ineffective due to civil strife, or whatever, they ended up with tyrants, or draconian laws to deal with. So we can see that what works best is minimal government, but only to the point where it can ensure that it continues to exist.
Now what about the idea of corporate government? Its an idea many FTL'ers here masturbate to. The two examples I can think of are The Congo Free State, and these weren't very positive examples of such governance. People will argue that since they governed an area they were not from, they had no motivation to be good to people they weren't related to.
A corporation with a wide latitude of duties and powers, and the muscle to back up insubordinate locals doesn't strike me as being any different than a government.