The Second Circuit has handed down an opinion on when nondisclosure orders served on an ISP comply with the First Amendment. The opinion both interprets and in some ways rewrites Congress's work with National Security Letters. Here's the key:

[We] rule that subsections 2709(c) and 3511(b) are unconstitutional to the extent that they impose a nondisclosure requirement without placing on the Government the burden of initiating judicial review of that requirement, and (5) rule that subsections 3511(b)(2) and (b)(3) are unconstitutional to the extent that, upon such review, a governmental official's certification that disclosure may endanger the national security of the United States or interfere with diplomatic relations is treated as conclusive.

Hat tip: Howard.