That is in a sense a garden-variety question of civil procedure. The legal filings that initiate civil suits must, after all, meet some minimum standards of cogency and legal sufficiency before plaintiffs can force defendants to submit to the information-gathering process lawyers call discovery, much less trial.
But the case of Javaid Iqbal, a Muslim man from Pakistan who used to be a cable television installer on Long Island, seemed freighted with something much larger, and many of the justices’ questions concerned whether the context in which the case arose, in the charged atmosphere in the fall of 2001, should alter or underscore ordinary legal principles.
Mr. Iqbal was among thousands of Muslim men rounded up after the Sept. 11 attacks. Some of them were considered to be “of high interest,” and they were held in a special housing unit of the Metropolitan Detention Center in Brooklyn.
While there, Mr. Iqbal said, he was subjected to daily body-cavity searches, beatings and extreme temperatures. He said he was kept in solitary confinement with the lights in his cell constantly on, that he was called a terrorist and a “Muslim killer,” and that he lost 40 pounds during six months in the special unit.
He eventually pleaded guilty to identity fraud and was deported to Pakistan.
His lawsuit contends that he was singled out for mistreatment based on his religion and national background. Mr. Ashcroft and Mr. Mueller, his lawsuit says, implemented the policies that led to the abuse and condoned it.
The two officials say that they are immune from suit, a contention rejected by the federal appeals court in Manhattan last year, at least at the most preliminary stage of the case. In the Supreme Court, the officials argued that Mr. Iqbal’s assertions that they were responsible for any abuses he suffered were speculative and lacked supporting factual allegations.
There was general agreement among the justices that the bar for starting a lawsuit, however low, must at least include plausibility. But the justices seemed divided over whether it was conceivable that the defendants here created or condoned a policy rooted in unlawful discrimination.
Justice David H. Souter said he considered plausible the claim “that the attorney general or the director of the F.B.I. was establishing a policy centered on people with the same characteristics as the hijackers.”
Solicitor General Gregory G. Garre, who represented the two officials, said such a characterization of the policy merely described “a perfectly lawful law enforcement program.”
Justice Ruth Bader Ginsburg suggested that a 2003 report from the Justice Department’s inspector general may “lend some plausibility” to Mr. Iqbal’s claims. The report found serious abuses by the facility’s personnel.
Mr. Garre urged the justices to ignore the report, saying it was outside the scope of the litigation. But he said the report had made findings helpful to his clients’ contention that their own actions, at least, were lawful.
Justice Stephen G. Breyer asked a hypothetical question: would a plaintiff be allowed to pursue a lawsuit against the president of Coca-Cola on the bare accusation that the president had personally put mice in soda bottles?
Other justices engaged the question, considering whether such a lawsuit would be subject to sanctions on the grounds that it was frivolous and whether the company’s president would have to submit to questioning under oath at a deposition.
“How are we supposed to judge whether we think it’s more unlikely that the president of Coca-Cola would take certain actions,” Chief Justice John G. Roberts Jr. asked Mr. Iqbal’s lawyer, Alexander A. Reinert, “as opposed to the attorney general of the United States?”
Mr. Reinert said that the answer was not to require more detailed accusations from his client but to require the defendants to provide evidence to establish whether they bore responsibility for what happened and whether they are entitled to immunity.
Mr. Garre countered that no such inquiry was needed because “common experience shows” that the attorney general and F.B.I. director “simply aren’t involved” in “granular decisions” about whom to detain and under what conditions.
Justice John Paul Stevens suggested that he was uneasy about lightly letting claims against high officials proceed, mentioning his majority opinion in Clinton v. Jones, the 1997 decision that allowed Paula Jones’s sexual harassment case against President Bill Clinton to go forward. A prediction in that decision about the burden the suit would place on the president — “it appears to us highly unlikely to occupy any substantial amount of petitioner’s time” — turned out to be incorrect.
Mr. Garre said the court’s decision in the case argued Wednesday, Ashcroft v. Iqbal, No. 07-1015, would have a broad impact. The appeals court, he said, had provided “a blueprint for civil plaintiffs who are challenging the implementation of important law enforcement policies to subject the attorney general, the director of the F.B.I. or other high-level officials to civil discovery based on conclusory and general and inadequate allegations.”