Well it's a real (if secret) court, so I assume it would be what normally happens for contempt of court.
[1] https://www.eff.org/deeplinks/2013/06/government-says-secret...
More broadly though, I don't understand how you can possibly have secret courts. Justice not only must be done but must be seen to be done, otherwise its not justice.
I don't understand how you can have secret courts either. It's a perversion of what this country was founded upon.
They are about masking injustice behind the veil of "law".
Since US is a country with long tradition of rule of law. The easiest way of subverting the rule of law is by subverting the concept of a judge and of a court.
There.
Edit: Way to mind-meld on the comments, team. Holy crap.