The Obama administration's top advocate at the Supreme Court will stand before the justices on Wednesday and defend Bush administration Attorney General John Ashcroft in an effort to help him stave off a civil suit filed by a man picked up by federal agents and held against his will.

Acting Solicitor General Neal Katyal will argue that Ashcroft should be immune from a lawsuit brought by a Kansas native who claims his Fourth Amendment rights were violated in 2003 when he was stopped from leaving the country and held in custody under severe conditions for more than two weeks.

Abdullah al-Kidd says Ashcroft’s leadership of the Bush Justice Department following the Sept. 11 terrorist attacks led to an unconstitutional practice of using material-witness laws as a pretext for arresting and detaining suspects without probable cause.

Lower courts, including the Ninth Circuit U.S. Court of Appeals, have ruled that Ashcroft is ineligible for the legal immunity normally offered to high-ranking government officials for actions that fall within their official duties.

"Seeking and obtaining a material-witness warrant is a core prosecutorial act, and a prosecutor is absolutely immune from any claims based on that act," Katyal wrote to the high court in his brief defending Ashcroft. In asking the court to hear the case, Katyal said that if the former attorney general is forced into a trial courtroom it will “substantially chill officers in the exercise of important governmental functions.”

ACLU lawyer Lee Gelernt is representing al-Kidd and says the Supreme Court has "never permitted the government to use a civil scheme or non-punitive justification for jailing people as a ruse to circumvent the constitutional protections afforded criminal suspects."

In 2003, federal investigators were supposedly interested in another man, Sami Omar Al-Hussayen, who was suspected of funneling money to a radical Islamic group. Agents used a material witness order to nab al-Kidd and said his testimony was crucial to the Al-Hussayen case.

In securing the warrant, a pair of FBI agents told a federal judge in Idaho that al-Kidd was on a one-way flight to Saudi Arabia. This was incorrect. Al-Kidd purchased a round-trip ticket, had family in the United States and had even helped the FBI in other investigations. This information was not part of the material witness warrant, which is only supposed to be used in extraordinary events to secure witness testimony.

Al-Kidd spent 15 days behind bars, was shackled during his movements and strip-searched multiple times. After his release from jail, al-Kidd was forced to stay in the region and to repeatedly stay in touch with the government. He was never charged with a crime and was also never called to testify against Al-Hussayen who wasn’t convicted.

Katyal says if the justices uphold the Ninth Circuit's ruling then all prosecutors across the country can be sued for issuing material-witness warrants. As to claims that Ashcroft can be held personally liable for directing agency policy, Katyal says high court precedent makes clear that "a plaintiff cannot defeat absolute immunity simply by alleging the existence of a broad policy concerning a prosecutorial action, otherwise plaintiffs could plead around such immunity in a variety of cases."

The case is Ashcroft v. al-Kidd.