The article is devoted to the analysis of the legal consequences for citizens of the Russian Federation who join the military service of the United States Armed Forces during the special military operation in Ukraine. The article examines the legal conflicts arising from the absence of international agreements between the Russian Federation and the United States in the field of military service and dual citizenship. Special attention is paid to the qualification of actions of Russian citizens serving in the U.S. Army and their liability under Russian legislation. The article analyzes criminal-legal and international-legal aspects, including the status of combatants under the Geneva Conventions.