I’m interested to know where this rule comes from (assuming this isn’t sarcasm), as that is not what the constitution states. In addition, why are you putting “due process” in quotes? You are familiar with what that means?

They are not owed anything, but the government has limits imposed on it by the Constitution. One of those limitations is due process before limiting someone's life or liberty. Deportation is one thing; shipping directly to a prison in El Salvador is something else entirely.