get the yearbooks downloaded and saved offline!
In the US, it derives from common law. There are good reasons and uses for it. But it can also be abused.
Just the intro to this article gives a decent understanding.
KEEP IT SECRET, KEEP IT SAFE: AN
EMPIRICAL ANALYSIS OF THE STATE
SECRETS DOCTRINE
http://www.stanfordlawreview.org/wp-content/uploads/sites/3/2015/05/67_Stan_L_Rev_1173_Cassman.pdf