If you say "Only citizens get due process" then all it takes is for the state to say "You're not a citizen" for you to lose your right to due process, because once you're labelled a non-citizen, you lose the right to defend against the claim.
If you say "Only citizens get due process" then all it takes is for the state to say "You're not a citizen" for you to lose your right to due process, because once you're labelled a non-citizen, you lose the right to defend against the claim.