Your point is only that the judges have been decreed to be trustworthy by various people. That's fine, and it's right to involve all three branches. But the proceedings being secret means no one has any evidence of their actual (as opposed to decreed) legitimacy. No one can reach any of the same conclusions by the same means. If a tree falls in a secret court and no one is there to hear it, does it make a sound?

The principle upon which courts themselves are founded is basically science - An assertion is only an assertion, and doesn't become legitimate unless it 1) has evidence backing it, and 2) survives adversarial argumentation. That which is proven and can't be disproven is deemed true. Where criminal accusations are concerned, it's what distinguishes a just verdict from mere arbitrary tyranny. That is the favor being done for prosecutors by defense attorneys: giving their wins legitimacy.

But the whole proceeding is public so that the people, the actual legitimate authority in the land, have access to the same evidence and the same arguments, and can reach the same conclusion reached by their agents and representatives in the court. The verdict is just and everybody knows it.

All I'm doing is applying the same principle to the FISA court itself. If they're so trustworthy and secure, so worthy of the job of interpreting laws, it should be no problem to present evidence to that effect, by opening the proceedings. Anything that needs to be done secretly kind of needs to shed the name of "court" and become e.g. "agency" or "department."