§ 958
Commission to serve against friendly nation
Official text prohibited actmental stateif conditionpenaltylegal term
Any citizen of the United States who, within the jurisdiction thereof, accepts and exercises a commission to serve a foreign prince, state, colony, district, or people, in war, against any prince, state, colony, district, or people, with whom the United States is at peace, shall be or imprisoned not more than three years, or both.
History: (June 25, 1948, ch. 645, 62 Stat. 745 (PDF, 39 MB); Pub. L. 103–322, title XXXIII, §330016(1)(I), Sept. 13, 1994, 108 Stat. 2147 (PDF, 52 MB).)
Simplified explanation
It is a federal crime for a U.S. citizen, while in the United States, to accept and act on a commission (official appointment) to serve a foreign power in war against a country the U.S. is at peace with.