The Constitution clearly states that it is Congress that has the power to declare war, not the president. The War Powers Act also clearly states that U.S. forces are to engage in hostilities only if the circumstances are “pursuant to (1) a declaration of war, (2) specific statutory authorization or (3) a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.”
Absent these criteria, the president has no authority to declare war.
Even if the president believes he has such authority, the War Powers Act goes on to require the president to seek congressional approval within 60 days of conflict.
No president is above the law or above the Constitution.
Our Founding Fathers were quite concerned about giving the power to declare war to the executive. They were quite concerned that the executive could rule like a king.