It's weird how unilateral designations without due process aren't enough to contravene the 2nd Amendment rights of a citizen....
....but, per Holder v. HLP, unilateral designations without due process are enough to revoke the 1st Amendment rights of a third party citizen.
So Person A being designated a terrorist doesn't prevent Person A from getting a gun, but Person A being designated a terrorist does prevent Person B from exercising their right to free speech to talk to Person A.
Of course, despite it being the most major attack on free speech rights in decades and being, of course, by the conservative court, you will literally never, ever see any of the new faux free speech advocates on the right talk about it.