Our colleagues at the Center for Democracy and Technology "joined other privacy groups and an ISP trade association in filing an amicus brief today [24 May] in support of the ACLU's challenge to the FBI's National Security Letter authority, which allows [the FBI] to obtain certain customer records from ISPs and other businesses without a court order." The text of CDT's brief is here.
ACLU's website gives the background of this case: "the American Civil Liberties Union has challenged the FBI’s unchecked authority to issue 'National Security Letters' (NSLs), which demand sensitive customer records from Internet Service Providers and other businesses without judicial oversight. Before the Patriot Act, the FBI could use the NSL authority only against suspected terrorists and spies. Thanks to Section 505 of the Patriot Act, the FBI can now use NSLs to obtain information about anyone..."
Here is the item we posted last month about this case.