This is technically correct (the worst kind of correct, in an ideologically-motivated thread people flock to seek emotionally-validating facts. As opposed to regular ones).

Reuters OP: "It was not clear what legal weight Trump's proclamation carried... legal experts said such a step lacked a basis in law"

See also:

https://www.voanews.com/a/usa_why-domestic-terrorism-not-spe... ("Why Domestic Terrorism Is Not Specifically Designated a Crime in US")

> "While U.S. law makes it a crime to provide “material support” to a foreign terrorist organization, there is no comparable law that makes domestic terrorism a federal crime, even though individual acts committed by domestic terrorists may be illegal."