And I'm not sure what you mean by revealing it would be meaningless. Once the key is known revealing the plain text is a simple matter for a one time pad.
I guess you never know when you will need an M-16 with a large clip to take down your own country's elected government.
Then why even try in the first place? Could it be that there is some worth in doing something despite the fact it may amount to nothing in the big picture of things?
Now a classmate of mine did something similar but didn't first check with the professors. He didn't get in trouble but was asked to rewrite one of the papers.
Who ever put the NSA together did a good job, at least in the sense of it accomplishing its mission.
As long as the courts are allowed to reinterpret a laws meaning these kind of things are inevitable.