When I was very young, I’d heard that any US citizen that went to fight with a foreign Army (like French Foreign Legion) could get in big trouble at home. Isn’t this a little worse than that??
Fighting in the French Foreign Legion was a totally different issue since it was an official arm of the France military.
ISIS, Al Qaeda etc are NOT official nation/governments. They are “terrorism movements” which have no standing in
international law.
Since Al Qaeda attacked the US (starting with the murder of Rabbi Meir Kahane in NYC in the 1990’s, then the first Twin Towers Bombing (6 killed, over a 1,000 wounded or injured), and then 9/11, not to mention the twin embassy bombings in Kenya and possibly Tanzania (in the late 80s), anyone who joined AQ or aided them in any way was officially designated as a “terrorist” (i.e. enemy combatant) and should have been completely under US military control when captured (instead of Clinton’s fairy program of treating the events as “criminal actions”, which was what Holder/Obama also di.
If you want acts of treason, the AQ/ISIS US citizens or residents quality, and so does a military tribunal and firing squad. And that would include Democrat politicians and traitors.