One thing that has been funny about the Mahmoud Khalil arrest has been commentators talking about the Trump Administration's shrewdness in arresting a permanent resident first, to test the First Amendment impact of the policy.
They weren't shrewd; they just didn't give a fuck. Citizenship for ultranationalists is colour-coded; every brown person is subject to expulsion, no matter what their papers say. Mahmoud Khalil was picked because of his leadership role, not his PR status.