Are you people insane? An agent of the executive branch of the federal government, deciding for himself, without a trial, or even an indictment, that US Citizens should be barred from the country? That's OK with you? Maybe these two are dangerous, but that's what we have a court system for. If these two have done something illegal, then they should be indicted and tried. If the government wants to coerce them into talking about any possible criminal activities in which they may have engaged, then this line comes into play : "nor shall be compelled in any criminal case to be a witness against himself?"
This is an absolutely outrageous overreach on the part of some federal agent, who should have been fired yesterday for this action.