10 U.S.C. § 7776
Emergency construction: fortifications
If in an emergency the President considers it urgent, a temporary fort or fortification may be built on private land if the owner consents in writing.
( Aug. 10, 1956, ch. 1041 , 70A Stat. 270 , § 4776; Pub. L. 91–393, § 5 , Sept. 1, 1970 , 84 Stat. 835 ; renumbered § 7776, Pub. L. 115–232, div. A, title VIII, § 808(d) , Aug. 13, 2018 , 132 Stat. 1839 .)