A site [1] mentions that student visas (F-1) may alter the protections of the first amendment, but doesn't go into any specific detail. Legal or not, if you're deported, it's ruinous, and forcing people to try to litigate against it is a practical win. Sounds like we need anti-SLAPP laws to protect us from the feds now...

[1]: https://www.freedomforum.org/non-citizens-protected-first-am...