10 U.S.C. § 162 — Combatant commands: assigned forces; chain of command

(a) Assignment of Forces. As directed by the Secretary of Defense, the Secretaries of the military departments must assign specified forces under their jurisdiction to unified and specified combatant commands, or to the United States element of the North American Aerospace Defense Command, to perform missions assigned to those commands. The Secretary of Defense must ensure these assignments are consistent with the force structure the President prescribes for each combatant command. A force not assigned to a combatant command or to the North American Aerospace Defense Command under this rule remains assigned to its own military department, for carrying out that department's Secretary's responsibilities under section 7013, 8013, or 9013 of this title, as applicable. A force assigned to a combatant command, or to the North American Aerospace Defense Command, may be transferred out of that command only by authority of the Secretary of Defense, and under procedures the Secretary prescribes and the President approves. Except as the Secretary of Defense otherwise directs, all forces assigned to a unified combatant command are under the command of that command's commander. This same rule applies to forces assigned to a specified combatant command only as the Secretary of Defense prescribes. (b) Chain of Command. Unless the President directs otherwise, the chain of command to a unified or specified combatant command runs from the President to the Secretary of Defense, and from the Secretary of Defense to the commander of the combatant command.