I hate to be a pest, but...

Help me sort this out. The president says that he isn't bound by actions of Congress because he has taken up the mantle of the "commander-in-chief," and as such he is permitted to take extraordinary steps since the commander-in-chief has greater latitude of choices than the president. The president becomes the commander-in-chief under the auspices of a congressional Declaration of War. However, despite the frequent use of the phrase "War on Terror," there has been no Declaration of War. So, how then is this president justified in claiming the powers of the commander-in-chief?