LARSEN, Circuit Judge. A fundamental tenet of our constitutional order is that the President’s authority “must stem either from an act of Congress or from the Constitution itself.” Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579, 585 (1952). The critical question in this case is whether the President heeded this rule when he ordered all federal agencies to include in their new contracts a provision obligating contract recipients to require their employees to wear face masks at work and be vaccinated against COVID-19. The President has claimed no inherent constitutional power here; instead, he maintains that the Federal Property and Administrative Services Act of 1949 authorized his order. The district court and a motions panel of this court concluded that the President likely exceeded his powers under that Act. We agree. We therefore affirm the district court’s decision to preliminarily enjoin the federal government from enforcing the mandate, but we modify the scope of the injunction.