Via FAS/Secrecy News: “If the President were to declare a national emergency in order to justify building a “wall” on the border with Mexico, there would be certain legal authorities that he could invoke to initiate construction operations. But the scope of those legal authorities is uncertain and would almost certainly trigger litigation to challenge their application, the Congressional Research Service said last week. “Whether these authorities — individually or in combination — extend to the construction of a border wall would present a reviewing court with several questions of first impression,” CRS said.

• See Can the Department of Defense Build the Border Wall?, CRS Legal Sidebar, January 10, 2019.
• On the other hand, the National Emergencies Act has been effectively invoked on two previous occasions to authorize military construction activity overseas (by Presidents George H.W. Bush and George W. Bush), CRS said in another new publication. See Military Construction Funding in the Event of a National Emergency, CRS Insight, updated January 11, 2019.”