Reply #4: Here we go: [View All]

[Hosnon]

"If a war be made by invasion of a foreign nation, the President is not only authorized but bound to resist force by force. He does not initiate the war, but is bound to accept the challenge without waiting for any special legislative authority."

- Justice Grier, for the majority, 67 U.S. 635 (1863).

It seems that the Supreme Court has read the Constitution to differentiate between offensive and defensive wars. In the case of the former, Congress must provide its authorization but in the case of the latter, the President is Constitutionally authorized to act.