The Christian Science Monitor has an article on a case relating to September 11th that is almost completely secret:

bq. It’s the case that doesn’t exist. Even though two different federal courts have conducted hearings and issued rulings, there has been no public record of any action. No documents are available. No files. No lawyer is allowed to speak about it. Period.
Yet this seemingly phantom case does exist – and is now headed to the US Supreme Court in what could produce a significant test of a question as old as the Star Chamber, abolished in 17th-century England: How far should a policy of total secrecy extend into a system of justice?

Via The Legal Reader