The facts are that, without a claim he had broken any law and as one of four seized as part of the F.B.I.'s wider ''Idaho probe,'' Mr. Kidd was arrested, strip-searched, shackled and jailed for 15 days -- handled like a suspect, not a witness. Against him and others, the Justice Department used the statute, Mr. Kidd's lawyers inferred and others must as well, ''to detain and investigate suspects for whom the government lacked probable cause of wrongdoing, and not to secure testimony.''

The government contends that Mr. Ashcroft didn't have to intend to use Mr. Kidd as a witness to detain him because the then-attorney general's motivation was irrelevant. But to the former prosecutors, it is ''settled understanding'' that the statute has ''no other legitimate purpose'' except to hold a witness for testimony.