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President's power to construct shit during a national emergency

10 U.S. Code § 2808 - Construction authority in the event of a declaration of war or national emergency

(a) In the event of a declaration of war or the declaration by the President of a national emergency in accordance with the National Emergencies Act (50 U.S.C. 1601 et seq.) that requires use of the armed forces, the Secretary of Defense, without regard to any other provision of law, may undertake military construction projects, and may authorize the Secretaries of the military departments to undertake military construction projects, not otherwise authorized by law that are necessary to support such use of the armed forces. Such projects may be undertaken only within the total amount of funds that have been appropriated for military construction, including funds appropriated for family housing, that have not been obligated.

(b) When a decision is made to undertake military construction projects authorized by this section, the Secretary of Defense shall notify, in an electronic medium pursuant to section 480 of this title, the appropriate committees of Congress of the decision and of the estimated cost of the construction projects, including the cost of any real estate action pertaining to those construction projects.

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President's power and procedure to declare national emergency via EO

50 U.S.C. § 1621 - U.S. Code - Unannotated Title 50. War and National Defense § 1621. Declaration of national emergency by President;  publication in Federal Register;  effect on other laws;  superseding legislation

(a)  With respect to Acts of Congress authorizing the exercise, during the period of a national emergency, of any special or extraordinary power, the President is authorized to declare such national emergency.  Such proclamation shall immediately be transmitted to the Congress and published in the Federal Register.

(b)  Any provisions of law conferring powers and authorities to be exercised during a national emergency shall be effective and remain in effect (1) only when the President (in accordance with subsection (a) of this section), specifically declares a national emergency, and (2) only in accordance with this chapter.  No law enacted after September 14, 1976, shall supersede this subchapter unless it does so in specific terms, referring to this subchapter, and declaring that the new law supersedes the provisions of this subchapter.