Comment by ilikehurdles

It has always been legal to deny visa/entry to people based on speech and affiliation. Pretty long list of evidence for that.

As for non-citizens lawfully present in the U.S., they have more First Amendment protections than those seeking entry, but still less than citizens.

All this can get visa holders deported:

1. Material support for terrorist organizations (even verbal/written advocacy.

2. Speech deemed to violate the terms of their specific visa category.

3. False statements to immigration officials.

4. (Most obviously) Criminal convictions stemming from speech acts (fraud, threats, etc.)