In the ensuing months [after 9/11] the FBI questioned more than 1,000 people with suspected links to the attacks in particular or to terrorism in general. Id., at 1. Of those individuals, some 762 were held on immigration charges; and a 184-member subset of that group was deemed to be “of ‘high interest’” to the investigation. Id., at 111. The high interest detainees were held under restrictive conditions designed to prevent them from communicating with the general prison population or the outside world. Id., at 112–113.

Respondent was one of the detainees. According to his complaint, in November 2001 agents of the FBI and Immigration and Naturalization Service arrested him on charges of fraud in relation to identification documents and conspiracy to defraud the United States. Iqbal v. Hasty, 490 F. 3d 143, 147–148 (CA2 2007). Pending trial for those crimes, respondent was housed at the Metropolitan Detention Center (MDC) in Brooklyn, New York.Respondent was designated a person “of high interest” to the September 11 investigation and in January 2002 was placed in a section of the MDC known as the Administrative Maximum Special Housing Unit (ADMAX SHU). Id., at 148. As the facility’s name indicates, the ADMAX SHU incorporates the maximum security conditions allowabl under Federal Bureau of Prison regulations. Ibid. ADMAX SHU detainees were kept in lockdown 23 hours a day, spending the remaining hour outside their cells in handcuffs and leg irons accompanied by a four-officer escort. Ibid.

Respondent pleaded guilty to the criminal charges,served a term of imprisonment, and was removed to his native Pakistan. Id., at 149. He then filed a Bivens action in the United States District Court for the Eastern District of New York against 34 current and former federal officials and 19 “John Doe” federal corrections officers. See Bivens v. Six Unknown Fed. Narcotics Agents, 403 U. S. 388 (1971). The defendants range from the correctional officers who had day-to-day contact with respondent during the term of his confinement, to the wardens of the MDC facility, all the way to petitioners—officials who were at the highest level of the federal law enforcement hierarchy.

....The 21-cause-of-action complaint does not challenge respondent’s arrest or his confinement in the MDC’s general prison population. Rather, it concentrates on his treatment while confined to the ADMAX SHU. The complaint sets forth various claims against defendants who are not before us. For instance, the complaint alleges that respondent’s jailors “kicked him in the stomach, punched him in the face, and dragged him across” his cell without justification, id., ¶113, App. to Pet. for Cert. 176a; subjected him to serial strip and body-cavity searches when he posed no safety risk to himself or others, id., ¶¶143–145, App. to Pet. for Cert. 182a; and refused to let him and other Muslims pray because there would be “[n]o prayers for terrorists,” id., ¶154, App. to Pet. for Cert. 184a. The allegations against petitioners are the only ones relevant here.

As to Ashcroft and Mueller:

John Ashcroft, the former Attorney General of the United States, and Robert Mueller, the Director of the Federal Bureau of Investigation (FBI). Ashcroft and Mueller are the petitioners in the case now before us. As to these two petitioners, the complaint alleges that they adopted an unconstitutional policy that subjected respondent to harsh conditions of confinement on account of his race, religion, or national origin.

Respondent’s account of his prison ordeal could, if proved, demonstrate unconstitutional misconduct by some governmental actors. But the allegations and pleadings with respect to these actors are not before us here. This case instead turns on a narrower question: Did respondent, as the plaintiff in the District Court, plead factual matter that, if taken as true, states a claim that petitioners deprived him of his clearly established constitutional rights. We hold respondent’s pleadings are insufficient.

....But even if the complaint’s well-pleaded facts give rise to a plausible inference that respondent’s arrest was the result of unconstitutional discrimination, that inference alone would not entitle respondent to relief. It is important to recall that respondent’s complaint challenges neither the constitutionality of his arrest nor his initial detention in the MDC. Respondent’s constitutional claims against petitioners rest solely on their ostensible “policy of holding post-September-11th detainees” in the ADMAX SHU once they were categorized as “of high interest.... To prevail on that theory, the complaint must contain facts plausibly showing that petitioners purposefully adopted a policy of classifying post-September-11 detainees as “of high interest” because of their race, religion, or national origin. This the complaint fails to do.

...the complaint does not show, or even intimate, that petitioners purposefully housed detainees in the ADMAX SHU due to their race, religion, or national origin. All it plausibly suggests is that the Nation’s top law enforcement officers, in the aftermath of a devastating terrorist attack, sought to keep suspected terrorists in the most secure conditions available until the suspects could be cleared of terrorist activity.

The Court also said:

It is important to note, however, that we express no opinion concerning the sufficiency of respondent’s complaint against the defendants who are not before us. Respondent’s account of his prison ordeal alleges serious official misconduct that we need not address here. Our decision is limited to the determination that respondent’s complaint does not entitle him to relief from petitioners.

The Court left open the possibility that Iqbal can amend his complaint:

The Court of Appeals should decide in the first instance whether to remand to the District Court so that respondent can seek leave to amend his deficient complaint.