18 U.S.C. § 958 : US Code - Section 958: Commission to serve against friendly nation

Search 18 U.S.C. § 958 : US Code - Section 958: Commission to serve against friendly nation

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 fined under this title or imprisoned
not more than three years, or both.