The sticky point is in the definition of “enemy combatant”. If an American joins an enemy army or terrorist group actively engaged in the violent overthrow of the American government seems, at first glance, a safe definition. However, the potential for abuse by the government is huge.
Rush Limbaugh is actively engaged in the overthrow of this specific group currently running the government. All that is missing is the “violent overthrow” part. Any “right wing violence” could be used as a pretext to shut him down and the connections could be fabricated particularly if he were to be shown to know the perpetrators.
Electing honorable representatives to government has never worked all that well recently. Few are to be found.
You can count on some left leaning prez eventually coming after FR thru some gov’t justification.