Zbigniew Brzezinski, the National Security Advisor to President Carter from 1977 to 1981, is a well-known hawk. But he's right with the progressive movement on Bush's Constitutional power to start a war with Iran [1].
First, in the absence of an imminent threat (and the Iranians are at least several years away from having a nuclear arsenal), the attack would be a unilateral act of war. If undertaken without a formal congressional declaration of war, an attack would be unconstitutional and merit the impeachment of the president. Similarly, if undertaken without the sanction of the United Nations Security Council, either alone by the United States or in complicity with Israel, it would stamp the perpetrator(s) as an international outlaw(s)
which is a polite way of saying War Criminal.