Currently a person goes before a judge, evidence is presented, and a ruling is made. This should all happens in a (more or less) transparent manner PRIOR to deportation. A court has decide that a person should be guilty of being here illegally and rule that they should be deported.
This is probably overly-simplistic, but I am not a lawyer. In general, our justice system is set up that punishments can only happen AFTER the accuser (in this case, the Fed Govt) has PROVEN that the accused is guilty.
I'm just going to add... the fact that the argument has to fall back on trying to litigate things like due process (something that's already established and is a foundational part of our justice system) should be a clear red flag that something is very wrong here.
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