Q In what circumstances, if any, would the president have constitutional authority to bomb Iran without seeking a use-of-force authorization from Congress? (Specifically, what about the strategic bombing of suspected nuclear sites -- a situation that does not involve stopping an IMMINENT threat?)
A. 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.
As for the specific question about bombing suspected nuclear sites, I recently introduced S.J. Res. 23, which states in part that “any offensive military action taken by the United States against Iran must be explicitly authorized by Congress.”
President Barack Obama on August 31, 2013 on decision to seek congressional authorization for Syria attack:
"I believe I have the authority to carry out this military action without specific congressional authorization"
The President refused to say what action he would take if Congress did not provide him with the requested authorization.
Amendment to resolution to authorize military force in Syria as offered by Senator Rand Paul, September 4, 2013:
"It is the sense of the Senate that the President does not have the 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."
Amendment voted down by Senate Foreign Relations Committee 14-4.
[Note: Cannot find breakdown on vote. Committee consists of 10 Democratic and 8 Republican senators.]