The Fourth Circuit is not ordering that he be given access to RB and KSM. The decision agrees that its in the Government's national security authority to decline to produce these witnesses for direct questioning. However, the Government has to provide "substitutions", which are summaries of statements made by KSM and RB to the defendant. The Gov't was already willing to do this, but the district court said the summaries weren't "reliable" (legal term of art) as evidence that would be submitted to the jury. The 4th Circuit said "wrong". The district court should not have rejected the compromise of presenting written summaries of the statements to the jury. The 4th Circuit said that summaries are appropriate, and gave the district court instructions on how to craft the summaries and how to instruct the jury concerning them as well.
It is a bit confusing, I know. But the key here is that the government doesn't have to produce the actual bad guys, it can use evidence refering to Sept. 11 (which the district court ordered them not to do as a sanction), and the government can seek the death penalty (again, the district court sanction said no death penalty because you refused to produce RB & KSM).
That's an excellent summary of what this decision means.
The district court should not have rejected the compromise of presenting written summaries of the statements to the jury. I don't see that quite the same. The disagreement is that the district court was wrong in determining that no compromise is possible with written summaries, and ordered the district court to work something out. That sounds reasonable.
They agreed that the summaries the government did produce basically twisted witness for the defense into being witness for the prosecution. The prosecutor tried to pull a fast one and got caught -- that's possibly what pissed off the district court enough to impose the sanctions it did.