I thought they did that. If not, why even bother having a list?
Declare war on ISIS, AQ, Muslim Brotherhood and every organization that espouses hate and violence against the USA. Then aggressively go after them on the battlefield at home and abroad, freeze or seize every financial account they have and hound them throughout the world. Put a “wanted dead or alive” poster out on every known member of these terrorist organizations throughout the country.
The problem with the list is in who controls it and who gets on the list. Veterans and Christians have been considered as terrorists so even a seemingly good idea like a watch list can be used to disarm the people.
Being on a list won’t prevent one from buying a gun. Otherwise every republican gun owner would get put on the list, every tea party member, and every member of a patriot group.
It’s taking away a right and convicting someone without proving anything, just saying they are a terrorist threat.