Justice Department officials said the secrecy provisions of the law prevented them from giving any details on their use.
Interestingly, conservatives are now using the discharge petition system to kill its secrecy provision.
The secrecy provisions were not included in the first draft of the law, which mainly concerned administrative matters such as bank supervision.
The secrecy provisions of banking havens make tracking down drug dealers and white-collar criminals far more difficult.
The new law changes two secrecy provisions governing child welfare investigations.
The study found that there might have been more than 70 material witnesses, but secrecy provisions prevented a definitive tally.
Fifteen other states in the South, the Midwest and the West have similar secrecy provisions, which under the Court's ruling today are now also invalid.
He sued for a declaration that the secrecy provision was unconstitutional and for an injunction against prosecution if he reported his own testimony.
They are asking only that the secrecy provisions be stricken on the ground that they are against public policy.
But Judge Merritt, who is the head of the conference's executive committee, said he personally opposed the secrecy provision.