Via Crooked Timber:
“The danger to political dissent is acute where the Government attempts to act under so vague a concept as the power to protect ‘domestic security.’ Given the difficulty of defining the domestic security interest, the danger of abuse in acting to protect that interest becomes apparent.”
That's a quote from United States v. United States District Court for the Eastern Dist. of Michigan et al, a 1972 Supreme Court decision. It is also, apparently, something whose release would be dangerous to our national security, since the Justice Department tried to redact it out of a letter written by the ACLU. Of course, the decision in its entirety has been publicly available since it was reached in 1972 , so it's a bit late for the government to try to squelch it.
Ten special bonus points to anyone who can give me a good reason why the publication of this quote is dangerous to national security. I'd offer ten more bonus points to anyone who can tell me why quotes like this should not be blocked, and ten more to anyone who can tell me why trying to make Supreme Court decisions inaccessible is a bad idea, but even though these are just imaginary bonus points, I don't think I could come up with enough of them to meet the demand.