See also Article I, Section 10: Powers of Congress

To define and punish Piracies and Felonies committed on the high Seas, and Offences against the Law of Nations;

To declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water

I included the paragraph before the war power to not the mention of the Law of Nations, which we have discussed before. Implied I suppose is the power to simply ignore the Law of Nations. Stan