] The Supreme Court yesterday declined to hear an appeal by
] civil liberties groups seeking access to basic data about
] hundreds of individuals detained by the federal
] government after the Sept. 11, 2001, terrorist attacks, a
] decision that allows officials to continue withholding
] the names of most detainees, as well as other information
] related to their arrests, indefinitely.

At least these ones were allowed a hearing. This capability combined with the ability to detain without hearing and deny access to counsel would be extremely dangerous.

Secrecy Allowed On 9/11 Detention (washingtonpost.com)