In the context of a qualified immunity analysis, the Court reversed the Ninth Circuit and held, in relevant part, that an objectively reasonable arrest and detention pursuant to a validly obtained material witness arrest warrant cannot be challenged as unconstitutional on the basis of allegations that the arresting authority had an improper motive. The complaint had alleged that in the aftermath of the September 11th terrorist attacks, then-Attorney General John Ashcroft authorized federal prosecutors and law enforcement officials to use the material-witness statute to detain individuals with suspected ties to terrorist organizations, that federal officials had no intention of calling most of these individuals as witnesses, and that they were detained, at Ashcroft’s direction, because officials suspected them of supporting terrorism but lacked sufficient evidence to charge them with a crime.