> US immigration law gives the president explicit right to do exactly what he did

Clearly the federal courts (six different district courts, if I've counted correctly) don't believe that the case is as open and shut as you do, or they wouldn't have aisued restraining orders against the EO, one of the explicit considerationa for which is likelihood of prevailing on the merits.

That one section of law appears to be a broad grant of power does not mean that that grant is not constrained by other provisions of law.

US law prohibits discriminating based on national origin except under specific circumstances. https://www.law.cornell.edu/uscode/text/8/1152

(A) Except as specifically provided in paragraph (2) and in sections 1101(a)(27), 1151(b)(2)(A)(i), and 1153 of this title, no person shall receive any preference or priority or be discriminated against in the issuance of an immigrant visa because of the person’s race, sex, nationality, place of birth, or place of residence.

If you read the many arguments made in the amicus curiae brief[1] that was at the top of HN here 12 hours ago, you would learn quite clearly that there is substantial precedent for requiring the executive branch to use its powers on a rational and discreet basis.

http://cdn.ca9.uscourts.gov/datastore/general/2017/02/06/17-...