My guess is they're going to try to deport legal citizens.

They'll have probably several months to deport a bunch of people before it gets to the supreme court, which will probably rule it's fine anyway. Remember that the body deciding if something is legal is 6 far right cranks and 3 liberals.

The idea is that in 30 days, newborn children of illegal immigrants will not be considered citizens due to the "and subject to the jurisdiction thereof" clause of the 14th amendment. This executive order will not revoke citizenship (ex post facto laws create another legal hurdle), but rather refuse to grant it. It's constitutionally grey and will almost inevitably need to go through the courts.

The amendment reads:

“All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.”

Their argument is that non-citizens are not "subject to the jurisdiction thereof" and therefore it doesn't apply.

So it'll go to the courts which will of course agree with Donny

The supreme court will decide most likely. That's the goal with most of these.