The DPA was enacted principally to assure U.S. military preparedness. But it defines “national defense” broadly to include “emergency preparedness” and “critical infrastructure protection and restoration.” The law “provides the President with an array of authorities to shape national defense preparedness programs and to take appropriate steps to maintain and enhance the domestic industrial base.” It authorizes him to prioritize the production of certain products and to “allocate materials, services, and facilities in such a manner, upon such conditions, and to such extent as he shall deem necessary or appropriate to promote the national defense.”
The DPA isn’t a blank check. The president cannot, for example, impose wage and price controls without additional congressional action, and he is often required to use carrots rather than sticks to achieve the law’s purposes. Nevertheless, because he is acting under an express congressional grant of authority, he is operating, as Justice Robert Jackson explained in his iconic concurring opinion in the “steel seizure” case Youngstown v. Sawyer (1952), at the apex of his legal and constitutional power.
Any state restrictions on commerce or personal behavior would have to yield to the federal imperative.