Marty Lederman informs us congress has three options-
1) Ask the U.S. Attorney to prosecute. The administration signaled yesterday that they wouldn't allow that to happen. (Again with that confusion the President seems to demonstrate between the role of the Attorney General and the Solicitor General. One serves the President, the other serves the people. )
2) They could have the Sergeant at Arms arrest and put on trial those administration officials directly in contempt.
3) They could file a civil suit. This would take forever to resolve.
I vote for option 2 but apparently this is the least likely of the bunch. Odd. Considering the administration's complete unwillingness to work with congress and total stonewalling I'd suggest it was the best solution.
(For the REAL story on what happened to the guy who had his arm cut off by Obi-Wan watch the video below. It's all just a sad misunderstanding.)