Sen. Zell Miller, D-Ga., says "American Taliban" John Walker should be stripped of his citizenship. Can they do that?
Maybe. A federal statute says that a citizen loses his citizenship by "serving in the armed forces of a foreign state if such armed forces are engaged in hostilities against the United States" but only if he does so "with the intention of relinquishing United States [citizenship]."
At one time, just fighting in an enemy army was enough to "expatriate" you (that's the technical term). But in 1967 and 1980 the Supreme Court held that a U.S. citizen "has a constitutional right to remain a citizen ... unless he voluntarily relinquishes that citizenship," so in 1986 the statute was changed.
So, Walker is still a citizen so long as he never formally told the U.S. government, "I quit"? Not so easy: The Supreme Court has held that the intention to give up citizenship could be inferred from a person's actions. Though voting in a foreign election or fighting in an enemy army can't be "treat[ed] ... as conclusive evidence of the indispensable voluntary assent of the citizen," it can be "highly persuasive evidence in the particular case of a purpose to abandon citizenship."
And the one lower court case that most directly applies this test is pretty bad (or, as we'll see, good) for Walker. In United States v. Schiffer (1993), a federal trial judge concluded that a U.S. citizen voluntarily surrendered his citizenship by fighting in the Romanian army in World War II, when Romania was at war with the United States.
"[N]o conduct," the court said, is "more demonstrative of an intent to relinquish American citizenship than voluntary service in the armed forces of a country at war with the United States." A federal appellate court case, Breyer v. Meissner (2000), supports this approach. So does a formal 1969 opinion by Attorney General Ramsey Clark.
In any case, the question is one of fact, left to the judge or jury: Did Walker continue serving in the Taliban army, while the Taliban was at war with the United States, with the intention of abandoning his U.S. citizenship? This is an odd sort of inquiry—people generally don't think in terms of "I am fighting in this war with a purpose to abandon my citizenship"—but that's what the law requires.
But Walker may actually want to claim he lost his citizenship. Right now, the nastiest charge Walker is facing seems to be treason. But only citizens (and residents) can be guilty of treason. Walker can claim he lost his citizenship as soon as the Taliban and the United States started fighting—there's precedent saying that "loss of nationality occur[s] immediately upon the commission of expatriating acts"—so he never had an opportunity to commit treason. In 1952, the Supreme Court seriously considered a similar theory, though it found the theory inapplicable to the particular facts of that case.
Of course, if Walker was an al-Qaida member or participated in terrorist attacks, then denying his citizenship would just get him out of the frying pan of a treason trial and into the fire of a military tribunal. Not so smart!
But if all he did was fight for the Taliban against the United States, then he wouldn't be covered by the tribunal order. Simply making war on the United States can get you killed on the field of battle, but it itself is not a crime: Once you surrender, you're a prisoner of war, and when the war is over, you get released. It only becomes a crime—treason—if you do it while a U.S. citizen.
Bonus question: Does it matter that Walker joined the Taliban before war broke out between it and the United States?
Not necessarily, because he did continue fighting for it when the United States engaged them in war. But he might avoid both loss of citizenship and a treason conviction by showing that he acted under duress.
Once the United States and the Taliban became enemies, he would argue, he had no choice: He'd be shot as a deserter or a spy if he tried to quit then. According to D'Aquino v. United States (1951)—the "Tokyo Rose" case—such a defense would work, but only if Walker could show that he "manifest[ed] a determination to resist commands and orders until such time as he is faced with the alternative of immediate injury or death. ... The person claiming the defense of coercion and duress must be a person whose resistance has brought him to the last ditch."
Not an easy burden to satisfy, but at least possible—if Walker did indeed want to quit (a big if) but couldn't. The showing that Walker would have to make to avoid loss of citizenship is probably less demanding.