Today, a federal appeals court ruled that former Attorney General John Ashcroft may be held liable for the wrongful detention of people held as witnesses after the 9/11 attacks. The ACLU filed the lawsuit. Snip from New York Times:

In a harshly worded ruling handed down Friday, a three-judge panel of the 9th U.S. Circuit Court of Appeals called the government's use of material witnesses after Sept. 11 "repugnant to the Constitution and a painful reminder of some of the most ignominious chapters of our national history." The court found that a man who was detained as a witness in a federal terrorism case can sue Ashcroft for allegedly violating his constitutional rights. Abdullah Al-Kidd, a U.S. citizen and former University of Idaho student, filed the lawsuit in 2005, claiming his civil rights were violated when he was detained as a material witness for two weeks after 9/11.

Appeals Court Rules Against Ashcroft in 9 / 11 Case (NYT)

The court also ruled that the federal material witness law can't be used to "preventively" detain or investigate suspects. The ACLU represents al-Kidd in the case, al-Kidd v. Ashcroft. Snip from their press release:

Writing for the majority in today's decision, Judge Milan D. Smith, Jr., wrote, "Framers of our Constitution would have disapproved of the arrest, detention, and harsh confinement of a United States citizen as a 'material witness' under the circumstances, and for the immediate purpose alleged, in al-Kidd's complaint. Sadly, however, even now, more than 217 years after the ratification of the Fourth Amendment to the Constitution, some confidently assert that the government has the power to arrest and detain or restrict American citizens for months on end, in sometimes primitive conditions, not because there is evidence that they have committed a crime, but merely because the government wishes to investigate them for possible wrongdoing, or to prevent them from having contact with others in the outside world. We find this to be repugnant to the Constitution, and a painful reminder of some of the most ignominious chapters of our national history."

Ashcroft Can Be Held Accountable For Post-9/11 Wrongful Detention, Court Rules (ACLU)