Proud Boys earned the designation in large part due to their actions in the US. Like most of our listed entities, they’re assessed globally. In its totality, their actions absolutely fit the 83.01 definition.
Yup, that tipped the scale, but Samidoun was already on the radar for a while as the continuation of / front for the Popular Front for the Liberation of Palestine, who have been listed since 2003.
The list of terrorist entities can be found here along with brief descriptions of why:
Currently listed entities The process of designating a terrorist entity can, of course, draw on classified security intelligence that’s not in the public domain.
That sucks, but I can totally see it. They can burn hot. Not unheard of for police tear gas or flash bangs to light things on fire… I remember a notorious drug house going up once because our tactical crew doing a search warrant landed a flashbang on the Sofa of Degeneracy, and it caught. Whole place and all the sought evidence burned to the ground.