Respondent al-Kidd alleges that, after the September 11th terrorist attacks, then-Attorney General Ashcroft authorized federal officials to detain terrorism suspects using the federal material-witness statute, 18 U. S. C. §3144. He claims that this pretextual detention policy led to his material-witness arrest as he was boarding a plane to Saudi Arabia. To secure the warrant, federal officials had told a Magistrate Judge that information “crucial” to Sami Omar al-Hussayen’s prosecution would be lost if al-Kidd boarded his flight. Prosecutors never called al-Kidd as a witness, and (as he alleges) never meant to do so. Al-Kidd filed suit pursuant to Bivens v. Six Unknown Fed. Narcotics Agents, 403 U. S. 388, challenging the constitutionality of Ashcroft’s alleged policy. The District Court denied Ashcroft’s motion to dismiss on absolute and qualified immunity grounds. The Ninth Circuit affirmed, holding that the Fourth Amendment prohibits pretextual arrests absent probable cause of criminal wrongdoing, and that Ashcroft could not claim qualified or absolute immunity.
Held:
