The Bill of Rights was added to the Constitution in 1791, not just to protect individual rights, but also to impose structural constraints on the federal government. These constraints sharply curb the powers granted in the unamended Constitution, divesting the federal government of some of the authority it would otherwise have. Thus, [the President’s] claim, based on the so-called “plenary power” doctrine, of nearly unlimited authority over immigration that is immune from judicial review has it exactly backwards. No federal power can override the Bill of Rights. To the contrary, the Bill of Rights limits federal power in every sphere, including immigration.
In particular, the Establishment Clause was originally understood as preventing federal regulation of religion in order to preserve state autonomy in this sphere. Prior to the enactment of the Fourteenth Amendment in 1868, a State could establish a state religion, favor some religions over others, favor religion generally over non-religion, or adopt a policy of nondiscrimination. Whatever it opted to do, the Establishment Clause disqualified the federal government from interfering in that choice. The authority of the States in the domain of religion has now been curtailed by the Fourteenth Amendment. But the constraints the Establishment Clause imposes on the federal government remain in their original form: The federal government can neither establish a national religion, nor engage in discrimination based on religious animus…..
The Executive Order, motivated by bias against Muslims, violates the Establishment Clause by disfavoring members of a particular minority religion in their efforts to enter the country. And because the Establishment Clause is a structural limitation on the power of the federal government, not just a source of individual rights, the Executive Order cannot be enforced even against foreign nationals, regardless of the extent of their connection to the United States.
The role of the Establishment Clause as a structural constraint on federal authority over immigration (as well as other federal powers) follows logically from the text, structure, and original meaning of the Bill of Rights. It is also consistent with this Court’s precedents, properly understood.