Legal scholars don't agree on whether Donald Trump's demagogic proposal to temporarily ban any of the world's 1.6 billion Muslims from entering the United States would be constitutional. That disagreement says more about the sorry state of the constitutional law profession than it does about the quality of Trump's proposal.
Over the course of American history the U.S. courts, including the Supreme Court, have "interpreted" the Constitution into a document that the nation's founders would hardly recognize. For example, when making his proposal for banning Muslims, Trump spoke favorably of Franklin D. Roosevelt's internment of Japanese-Americans (and Japanese residents) during World War II. This episode has been properly recognized by historians as one of the darkest in American history, yet the Supreme Court at the time had no problem with this flagrant violation of the Fifth Amendment's due process clause that no person (the Constitution does not even require a person to be a citizen to get this protection) shall "be deprived of life, liberty, or property, without due process of law" or the Sixth Amendment's requirements of a jury trial.
The incarceration of Japanese-Americans has bearing on the current case of Muslims, because it derives from the same irrational fear that gripped the nation after the Japanese attacked Pearl Harbor--only now, the excuse doesn't exist that today's threat seems as dire. Even then, in the actual war zone of Hawaii, the restrictions on Japanese-Americans and Japanese residents were less harsh than in the continental United States, thousands of miles from Hawaii. Furthermore, two federal government studies, including one by the FDR White House, had shown that Japanese-Americans and Japanese residents were loyal to the United States and posed no security threat. FDR, always the consummate politician, reprehensibly incarcerated more than 100,000 innocent people in prison camps merely to respond to the war hysteria of the citizens of California, an important electoral state. Many of these Japanese-Americans lost everything. The Supreme Court also upheld bans on the entry of Chinese laborers in the late 1800s--another dark episode in American history.
Eric Posner, a conservative legal scholar from the University of Chicago--who purports, as many conservatives do, to be standing up for the founders' vision of the Constitution--says of Trump's ban on Muslims: "I don't actually think it would be unconstitutional. The president has a huge amount of discretion under the immigration statute." Posner also reportedly said that the same protections given citizens do not apply to people who are neither American nor in the United States.
On the first point, it is clear that the courts have given Congress and the president broad discretion on immigration issues. On the second point, most legal scholars do agree with Posner that a ban on allowing Muslim U.S. citizens to enter the country would be unconstitutional.
Yet historically, the courts have probably let the Congress and the president usurp too many rights under the immigration statutes, as the ban on Chinese laborers indicated. The federal government does have control over immigration, but in this case the First Amendment, which states that the "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof." The Constitution, in its various parts, regularly distinguishes between "citizens" and "persons" or "people". Later on in the First Amendment it speaks of "people," not "citizens," which should lead the common reader to infer that--no matter what the courts, or the constitutional scholars who usually populate them, say--citizens have no greater standing here than non-citizens. A temporary ban on Muslims also violates at least the spirit of the equal protection clause of the Fourteenth Amendment, which prohibits state governments from denying any "person" the equal protection under the law.
Legalities aside, Trump's proposal is moronic, because banning 1.6 billion Muslims to stop a few terrorists, who just happen to be Muslims, doesn't solve the problem. Why didn't Trump advocate banning incoming Christians after the recent lethal attack on the Planned Parenthood facility in Colorado Springs? Furthermore, although extreme minority interpretations of Islam are part of the Islamist terrorism problem, the main reason they attack the United States and its allies is just the latest manifestation of the reaction to the West's post-World War I colonialist and neo-colonialist foreign policy toward the Middle East region. Even with the carnage of the 9/11 attacks and the much lesser death toll of the San Bernardino shootings, the West has killed many more Middle Eastern Muslims for dubious reasons than vice versa.
Trump's solution is just a more extreme version of the denial that the West has shown since 9/11 that radical Islamist terrorism is retaliatory in nature. The reality for Middle Eastern Muslims has become what George W. Bush claimed after 9/11: the United States needs to fight them over there so it doesn't have to fight them over here. For Middle Eastern Muslims, they are beginning to strike over here to ultimately get the United States to withdraw from over there. Thus, Trump's proposal is just one more example of a false solution based on hysteria. The real solution is not to live in such fear in America--retaliatory Islamist terrorist attacks will end at home if the U.S. and allied governments quit needlessly poking the hornet's nest in the Middle East, which citizens should pressure their governments to do.