10 U.S.C. § 123b

(a) End-Strength Limitation .— No funds appropriated to the Department of Defense may be used to support a strength level of members of the armed forces assigned to permanent duty ashore in nations outside the United States at the end of any fiscal year at a level in excess of 203,000. (b) Exception for Wartime .— Subsection (a) does not apply in the event of a declaration of war or an armed attack on any member nation of the North Atlantic Treaty Organization, Japan, the Republic of Korea, or any other ally of the United States. (c) Presidential Waiver .— The President may waive the operation of subsection (a) if the President declares an emergency. The President shall immediately notify Congress of any such waiver.