In 2007 former constitutional law professor Barack Obama answered a question about the President’s authority to unilaterally cause the U.S. to take military action.

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?)

OBAMA:  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.

Obama was also asked about the ability of the federal government to conduct searches without a warrant.

Does the president have inherent powers under the Constitution to conduct surveillance for national security purposes without judicial warrants, regardless of federal statutes?

The Supreme Court has never held that the president has such powers. As president, I will follow existing law, and when it comes to U.S. citizens and residents, I will only authorize surveillance for national security purposes consistent with FISA and other federal statutes.