Even bigger question: what then?
Say you deport a citizen of Mexican origin to Mexico. Can’t they just, you know, go back? They’re citizens, with a passport/id.
The only alternative is to strip them (at least de facto) of their citizenship, which is literally a Hitler move (https://de.m.wikipedia.org/wiki/Gesetz_über_den_Widerruf_von_Einbürgerungen_und_die_Aberkennung_der_deutschen_Staatsangehörigkeit, only a German source, unfortunately).
I’m completely out of the loop here, what’s the point of testing in the first place? Maybe I’m too European for that, but this seems extremely intrusive for no reason.