I previously criticized GOP complaints that Obama did not seek a formal declaration of war or permit congressional debate on the issue. However, I did not intend to address the propriety of Obama's having failed to seek any form of congressional approval. Obama's decision to forgo the sort of legislative mandate which George W. Bush sought and received has puzzled many - especially in light of Obama's own words on the subject from 2007.
The President does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.
As Commander-in-Chief, the President does have a duty to protect and defend the United States. In instances of self-defense, the President would be within his constitutional authority to act before advising Congress or seeking its consent. History has shown us time and again, however, that military action is most successful when it is authorized and supported by the Legislative branch. It is always preferable to have the informed consent of Congress prior to any military action.
A commenter on this site suggested:
Obama doesn't feel he needs Congressional authorization when he's just received authorization from a source he deems more legitimate, id est, the United Nations.
It does seem to be inescapably obvious that approval by the Arab League and United Nations was sufficient for Obama to conduct military action. U.S. approval was deemed unnecessary. Unless Obama's views on the inherent war powers of the presidency have evolved, he must either believe that there was no time to consult Congress or intended to demonstrate the authority of international law within the context of the American Constitution.
The latter would be the most serious political declaration of the Obama presidency.