Thanks for the correction. Seemed so obvious.
https://www.law.cornell.edu/uscode/text/18/1652
Whoever, being a citizen of the United States, commits any murder or robbery, or any act of hostility against the United States, or against any citizen thereof, on the high seas, under color of any commission from any foreign prince, or state, or on pretense of authority from any person, is a pirate, and shall be imprisoned for life.
(June 25, 1948, ch. 645, 62 Stat. 774.)