In this Feb. 14, 2011 file photo, Abdullah al-Kidd is seen in Los Angeles. The Supreme Court ruled Tuesday that former Attorney General John Ashcroft cannot be personally sued over his role in the post-9/11 arrest of an American Muslim who was never charged with a crime. By a 5-3 vote, the court said Ashcroft did not violate the constitutional rights of Abdullah al-Kidd.

Washington ? The Supreme Court on Tuesday threw out damage claims against former Attorney General John Ashcroft over an American Muslim’s arrest, but four justices said the case raises serious questions about post-9/11 detentions under a federal law intended to make sure witnesses testify.

The justices were unanimous, 8-0, in holding that Ashcroft cannot be personally sued over his role in the arrest of Abdullah al-Kidd in 2003. The court sets a high bar for suing high-ranking officials, and all the justices agreed al-Kidd did not meet it, even though he was never charged with a crime or called to testify in the terrorism-related trial for which he ostensibly was needed.

Al-Kidd contended that his arrest under the material witness statute had a more sinister motive that violated his constitutional rights — federal authorities suspected him of ties to terrorism but lacked evidence that he committed or was planning a crime. And, he said, Ashcroft blessed the use of the law in the days after the Sept. 11, 2001, attacks to take suspected terrorists off the street.

A five-justice majority absolved Ashcroft of any wrongdoing. “We hold … that Ashcroft did not violate al-Kidd’s Fourth Amendment rights,” Justice Antonin Scalia said in his majority opinion. The five justices in the majority on this aspect of the decision are all Republican appointees.

But one of those justices, Anthony Kennedy, wrote separately to stress the narrowness of the decision. Kennedy said the case left unresolved how broadly the government may use the material witness statute, which has existed in one form or another since 1789.

Justices Stephen Breyer, Ruth Bader Ginsburg and Sonia Sotomayor said they would have resolved the case solely on the ground that Ashcroft could not be sued, whether or not al-Kidd’s arrest violated the Constitution. Justice Elena Kagan did not participate in the case because she worked on the issue when she was solicitor general.

Sotomayor said no previous case involving allegedly unlawful arrests “involved prolonged detention of an individual without probable cause to believe he had committed any criminal offense.”

Ginsburg said al-Kidd’s “ordeal is a grim reminder of the need to install safeguards against disrespect for human dignity, constraints that will control officialdom even in perilous times.”

The opinions are no aid to al-Kidd or roughly six dozen other men, almost all Muslims, who were arrested and held in the months and years after Sept. 11 under the material witness statute. But federal judges asked to issue such warrants in the future might take account of what the justices said Tuesday.

The opinions “shine a light on the problems of the material witness statute and make clear that federal judges must carefully scrutinize a request for a material witness warrant,” said the American Civil Liberties Union’s Lee Gelernt, al-Kidd’s lawyer.

Born in Kansas, Al-Kidd is a former University of Idaho football star who now teaches English to college students in Saudi Arabia. He was headed to Saudi Arabia on a scholarship in 2003 when federal agents arrested him at Washington-Dulles International Airport.

The sworn statement the FBI submitted to justify the warrant had important errors and omissions. The $5,000 one-way, first-class seat that the agents said al-Kidd purchased was, in reality, a coach-class, round-trip ticket. The statement neglected to mention that al-Kidd had been cooperative or that he was a U.S. citizen with a wife and children who also were American.

After the arrest, he was held for 16 days, during which he was strip-searched repeatedly, left naked in a jail cell and shower for more than 90 minutes in view of men and women, routinely transported in handcuffs and leg irons, and kept with people who had been convicted of violent crimes.

Even after Tuesday’s ruling, al-Kidd still has claims pending against the FBI agents who obtained the material witness warrant used to arrest him. Al-Kidd has separately reached settlements with Virginia, Oklahoma and Idaho jail officials over his treatment. A federal judge in Oklahoma ruled the strip searches al-Kidd endured at the federal jail in Oklahoma City “were objectively unreasonable and violated the Fourth Amendment.”

The lawsuit against Ashcroft, attorney general from 2001 to 2005, stemmed from comments he made shortly after 9/11 that the government would preventively detain people suspected of terrorist ties, even if it had no evidence they committed a crime.

The 9th U.S. Circuit Court of Appeals in San Francisco, in allowing the lawsuit against Ashcroft to go forward, said using the material witness statute as a pretext to detain someone was a violation of the Fourth Amendment. The appeals court also said Ashcroft should have known that such detentions would violate the law.

But the high court has said that an official must be tied directly to a violation of constitutional rights and must have clearly understood the action crossed that line to be held liable. No attorney general has ever been held personally liable for official actions.