President Donald Trump is prohibited from pre-emptively attacking North Korea without express congressional authorization to retaliate against Chairman Kim Jong-un’s verbal thunderbolts. But the president may attack unilaterally in self-defense to answer sudden North Korean aggression with the use of military force proportionate to its provocation.
The War Powers Resolution of 1973 (WPR) does not disturb these twin precepts. Section 8 (d) (1) of the WPR declares: "Nothing in this joint resolution - (1) is intended to alter the constitutional authority of the Congress or of the President ..."
Article I, section 8, clause 11 of the Constitution empowers Congress "to declare war."
Every participant in the Constitutional Convention and state ratification debates understood the Declare War Clause to prohibit the president unilaterally from crossing the Rubicon from peace to war. The president was, however, empowered to repel sudden attacks. At the convention, James Madison, father of the Constitution, prevailed in proposing that congressional power "to declare war" replace a power "to make war" ... "leaving to the Executive the power to repel sudden attacks [in self-defense]."
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But NOTE WELL that others, such as Obama ad-Dajjal, have circumvented this prohibition by using US obligations under the NATO treaty as a pretext for making war on Libya and Syria, etc.
Frankly ALL PRESIDENTS should have their war making powers removed ... not just Trump.