After an appeal is denied, or a requester is still not satisfied with the response, a lawsuit for judicial review can be filed.
This is ongoing litigation in DC District Court.
The DoJ (acting for NASA) submitted a motion for summary judgement:
Motion for Summary Judgment by DoJ in CEI vs NASA (2010)
which CEI responded to:
CEI response to DoJ motion for summary judgment in CEI vs NASA (2010)
and DOJ replied to:
DoJ reply to CEI in support of motion for summary judgement in CEI vs NASA (2010)
Motions are currently under consideration.