Trump's exclusion of aliens from specific countries is legal

Put aside that Trump is principally relying on his inherent constitutional authority, and that the class restriction he has directed is based on national-security, not racial or ethnic considerations. Trump’s executive order also expressly relies on an Obama-era provision of the immigration law, Section 1187(a)(12), which governs the Visa Waiver Program. This statute empowers the executive branch to waive the documentation requirements for certain aliens. In it, Congress itself expressly discriminates based on country of origin.

Under this provision, Congress provides that an alien is eligible for the waiver only if he or she has not been present (a) in Iraq or Syria any time after March 1, 2011; (b) in any country whose government is designated by the State Department as “repeatedly provid[ing] support for acts of international terrorism”; or (c) in any country that has been designated by the Department of Homeland Security as a country “of concern.”

So, not only has Congress never repealed the president’s sweeping statutory power to exclude classes of aliens from entry on national-security grounds; decades after the 1965 anti-discrimination provision touted by Bier, Congress expressly authorized discrimination on the basis of national origin when concerns over international terrorism are involved. Consequently, by Bier’s own logic, the 1965 statute must be deemed amended by the much more recent statute.