If labeled an enemy combatant it would move it to military court. Basically turning it into a foreign matter. To me anyone doing such a thing should not be considered an American citizen, within the act you are denouncing your citizenship.
After the war, we deported a number of women for having affairs with German soldiers. They were Norwegian citizens, born in Norway to Norwegian parents. They were stripped of their citizenship, and they were deported to a Germany.
This was, of course, perfectly legal. Oh, wait, no, it wasn't. It was completely illegal. Just like the mass deportations of communists during the red scare was illegal and FDRs internment of American citizens with Japanese ancestry was also illegal.
Labeling an American citizen an enemy combattant is making up a fake excuse do deny him or her habeas corpus. It is also completely stupid and about as warranted as eating a sledge hammer in order to become more sturdy.
I don't know if you recall, but we had an event in Oslo and on a small island about one and a half year ago. Sure was painful going through that trial, I promise you. But it was worth it, just like it was worth it prosecuting Vidkun Quisling in a proper way. It's because our societies are above the wrath of the totalitarianist state.
The principle of a fair trial to anyone for any crime is about as complicated as the principle of giving every single citizen the same vote in an election.
And to be honest, it is purile to say the least to even suggest that anyone should be beyond a fair trial. A free society isn't worth the ink it's founded on if you start selectively chopping out the bits that don't fit you.
Perhaps it's time for a new constitutional ammendment banning critisism of the government as well.
I keep hearing that liberals teach accepting others opinions, then I don't see it in action.
The principle idea of liberalism is tolerance to the freedom of others, that does include the principle that people can form, frame and express opinions, even if they're quite frankly so weird and silly they make as much sense as trying to herd cats. But I'd still take a bullet to defend your right to believe utter drivel. And that's not (just) a clich?, I actually believe that.