It's not so much a government. Each pure blood has their own vampiric followers, those they have changed (and vampires they have changed) follow them closely. Although they value the pure blood's race, they don't necessarily have to assist another pure blood in danger. Pure bloods have killed each other before between disputes.
If a pure blood is in danger upon being attacked, another pure blood may look upon them as being dumb or stupid for getting in a situation. Thus, they don't assist and let action take it's course. Pure bloods have a mind of their own and only they choose who to help and who not to. They have no higher power other then then themselves, so they receive no orders upon who to help or kill. The only thing pure bloods agree upon is keeping the vampire secret.
does this make sense?