There were some habeus cases filed (believe it or not) on behalf of German or Italian POW's in WWII who were held in POW camps in the US but who had dual citizenship. I know the cases were dismissed, but I can't recall the reasons why (probably because there was no criminal charge, and/or because their 'citizenship' claim was not recognized).
The U.S. didn't recognize "dual citizenship" in those days (and should not now -- Israel and the lobby are to blame for that one), so that anyone who swore a military oath on enlistment in a foreign army (or the Knesset, in Rabbi Meir Kahane's case) became a foreign national and gave up U.S. citizenship. If my sister, born in Canada, had exercised the Canadian franchise or enlisted in the Canadian Forces before she voted in the U.S., she'd be a Canadian citizen today.
The Italians and Germans who claimed U.S. citizenship had no shot at getting a judge to sustain them.
I agree with you and saganite, this is a conservative judge sticking it in the liberal Supremes' ears.
I hope Ruth Ginzburg and David Souter live at least 15 minutes longer than it takes to inaugurate the next GOP President.