If Obama attacks without an actual declaration of war, it will be a violation of the Constitution — just like it was when Bush did it, when Clinton did it, when the other Bush did it — even when Reagan did it.
Since the end of WW II, every time we used our military against another nation, this nation has acted outside the confines of the Constitution. The Constitution is the Social Contract which formed this nation, and under which this nation continues to exist. This means the Constitution is the supreme law of our land. This also means that the government has violated the Social Contract every time it used military power since WW II – and the people have done nothing about it. If one side of a contract continuously breaks their terms of the agreement and the second Party doesn’t object and seek restitution, eventually, it is assumed that the second Party agrees to the violation. At that point, the Party that has been violating the contract either assumes those violations as rightfully theirs, or the contract is considered null and void all together. This happens with republics, as well. If we allow our government to continuously violate the Constitution, sooner or later, it will either assume those violations are part of its authority or, more likely, that the Constitution no longer applies to it or its actions. When that happens, we will have the tyranny our founders warned us about, and it will have come from exactly the place our founders told us it would: from within our own borders – from us.
The Constitution grants the authority to declare war and to raise an Army to Congress and only to Congress: