I'm aware that Khalil's case involves the McCarthyesque Immigration and Nationality Act because he's a lawful permanent resident where non-citizens are being processed under things like the Alien Enemies Act. Let's not get lost in the weeds here.

> So this is an interesting legal question because non-citizens definitely do not have complete free speech protections

All persons on American soil are entitled to constitutional protections [1].

Consider the implications if they're not entitled to due process, for example. The government could detain a citizen and deport them without a hearing to a foreign country and then, when told to return them by a court, claim they have no jurisdiction over that foreign country. The administration is actually using the last argument.

You might say "they can't deport citizens". They are in effect arguing they can and there's no remedy for you if you're mistakenly deported, possibly indefinitely detained.

That's what due process is for: to establish if there is a lawful basis for the deportation.

[1]: https://firstamendment.mtsu.edu/article/aliens/