It is also perfectly legal to hold a trial where he is represented by counsel, rather than physically present. So if they were serious about trying to achieve 'justice', they could. But they're not. They're serious about trying to get him back on US soil. Which doesn't really speak well of their intentions.
I'm pretty sure if they did this, we would have a bunch of posts on this very forum decrying the trial as a "show trial", where Snowden does not have the ability to speak for himself or present his own defense. Whatever counsel they choose would be dismissed as a government puppet, and the result would have no impact on how people think.
