It's not.
The rubicon has already been crossed. If you asked some of the framers of the US constitution - beyond all other factors, unelected powers etc - what was the one defining trait of the government structure they wished to avoid; they'd have replied with arbitrary imprisonment and the suspension of due process.
Please don't take my word for it, hear it from the Prosecutor's Prosecutor. The SCOTUS justice, former AG and former USSG who led the American prosecution against the Nazis at Nuremberg, Robert H. Jackson,
No society is free where government makes one person's liberty depend upon the arbitrary will of another. Dictatorships have done this since time immemorial. They do now. Russian laws of 1934 authorized the People's Commissariat to imprison, banish and exile Russian citizens as well as "foreign subjects who are socially dangerous."' Hitler's secret police were given like powers. German courts were forbidden to make any inquiry whatever as to the information on which the police acted. Our Bill of Rights was written to prevent such oppressive practices. Under it this Nation has fostered and protected individual freedom.
The Founders abhorred arbitrary one-man imprisonments. Their belief was--our constitutional principles are-that no person of any faith, rich or poor, high or low, native or foreigner, white or colored, can have his life, liberty or property taken "without due process of law." This means to me that neither the federal police nor federal prosecutors nor any other governmental official, whatever his title, can put or keep people in prison without accountability to courts of justice. It means that individual liberty is too highly prized in this country to allow executive officials to imprison and hold people on the basis of information kept secret from courts. It means that Mezei should not be deprived of his liberty indefinitely except as the result of a fair open court hearing in which evidence is appraised by the court, not by the prosecutor
There is a reason why citizenship was not a requirement for receiving due process under the law. Citizenships are bestowed by the government. They can be taken away by the government. The framers held certain rights to be unalienable from human beings - something that no government can take away, and that was the right to not be unjustly detained for your beliefs, your behavior, your dress, your religion or composure.
Suspending due process for anyone is fundamentally un-American. But we have crossed that threshold. What comes next is fairly inevitable - if the process isn't stopped now.