Let me quote US vice President Joe Biden.
I was Chairman of the Judiciary Committee for 17 years. I teach separation of powers in Constitutional law. This is something I know. So I brought a group of Constitutional scholars together to write a piece that I'm going to deliver to the whole United States Senate pointing out that the president HAS NO CONSTITUTIONAL AUTHORITY to take this country to war against a country of 70 million people unless we're attacked or unless there is proof that we are about to be attacked. And if he does, I would move to impeach him.
from this article
http://www.theatlantic.com/politics/archive/2013/08/joe-bidens-case-that...