Today's ruling affirms the court’s September 2009 ruling that found that the material witness law may only be used when an individual is genuinely sought as a witness and where there is a real risk of flight. The court ruled that the law does not allow an end-run around the constitutional requirements for arresting someone suspected of a crime. Ashcroft had appealed the ruling.

The material witness statute was enacted in 1984 for specific reasons. As Yale Law Prof Jack Balkin wrote in 2003:

The federal material witness statute allows federal officials to detain people whose testimony is thought to be material to an ongoing criminal investigation for the purpose of testifying before a grand jury or in a criminal trial. The material witness statute, passed in 1984, was used rather infrequently before 9/11, mostly in drug smuggling and organized crime cases.

Following 9/11 the Justice Department has used the statute to round up an unspecified number of people and hold them indefinitely without trial.

The ACLU said today:

“Former Attorney General Ashcroft deliberately distorted the federal material witness law to allow the detention of innocent people. As the primary architect and overseer of this policy that so clearly circumvented the Constitution, he should be held personally liable.”

Who is al-Kidd? A U.S. born American citizen:

Al-Kidd, a U.S.-born American citizen, was on his way to Saudi Arabia to study when he was unlawfully detained and arrested in Washington's Dulles Airport on March 16, 2003 as a material witness in the trial of Sami Omar Al-Hussayen. For 16 days, al-Kidd was held in heightened-security units of various jails and shackled whenever moved. He was eventually released under onerous conditions that included confining his travel to four states, surrendering his passport and reporting to probation officers. Al-Kidd was held for more than 13 months under these conditions without ever being charged with any crime or asked to testify.

At the time of his arrest, al-Kidd had already shown that he was not a flight risk and would cooperate as a witness. He had voluntarily met with the FBI repeatedly, never missing a scheduled appointment. For six months prior to his arrest, al-Kidd had not been contacted by the FBI, and he had never been told that he was prohibited from traveling abroad to pursue his studies.

From the three judge decision in September (one of whom was appointed by Reagan and one by Bush):

"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."

Everyone but Ashcroft settled the case:

The ACLU lawsuit names Ashcroft, the United States and several federal agents as defendants. Local, state and federal officials in Virginia, Oklahoma and Idaho already settled claims against these parties.

More information about the case, al-Kidd v. Ashcroft, including the ACLU's complaint, the court’s September 2009 ruling and other legal documents are available here.

The ACLU and Human Rights Watch also have this 2005 report on the misuse of the material witness statute, Witness to Abuse.

Some of our prior coverage of the case is here (2004) and here (2006.)

(As an aside, AG Michael Mukasey wasn't any better as a judge in post-9/11 New York. Here's a New York Times article with criticism of his policy regarding material witnesses. We wrote about it several times, especially the case of Osama Awadallah, see here and here.)