According to this Washington Post article (courtesy of BoingBoing), provisions in the Patriot Act are preventing the ACLU from revealing details about their lawsuit challenging other provisions in the law.
I apologize for linking to a Washington Post article. I do not subscribe to their required, free registration scheme (yes, I registered at the New York Times, but that was a long time ago), nor do I expect you to. But how to get around their Orwellian motto of "Register Now. It's Free and It's Required?"
However, if you were to do a Google search on said Washington Post link, and then using the link to the Google search page, washingtonpost.com will deliver up the article, registration be damned.