Democracy
Democracy works only if it is restrained by an overriding set of objective principles. Something that says, "this particular thing is not subject to majority rule." For example, it should not be possible for a majority vote to legalize slavery again.
The Constitution still serves this function in the U.S., although a number of glaring loopholes have been drilled through it to advance centralized authority.
Something like that has to be the underpinning of any form of government in Iraq as well, to prevent the abuses that a pure democracy would be subject to.