Senators Rand Paul (R-Kentucky) and Mike Lee (R-Utah) have done what no Republican has done since the day Harry Truman sent US troops to Korea without congressional authorization: challenged the authority of the President to unilaterally commit the nation to war.
...The U.S. Senate held a vote on a sense of the Senate resolution, introduced last week by Senator Rand Paul (R-Ky.). The language of the resolution simply quoted then-Senator and presidential candidate Barack Obama’s words 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.” The measure aimed to put the Senate on record affirming Congress as the body with constitutional authority on matters of war. The motion was tabled, 90-10.
"The President does not have the power to unilaterally authorize a military attack in a situation that does not involve an actual or imminent threat to the nation."