Facts: A California court's order sentencing respondent Knights to probation for a drug offense included the condition that Knights submit to search at anytime, with or without a search, arrest warrant, or reasonable cause, by any probation or law enforcement officer. Subsequently, a sheriff's detective, with reasonable suspicion, searched Knights's apartment. Based in part on items recovered, a federal grand jury indicted Knights for conspiracy to commit arson, for possession of an unregistered destructive device, and for being a felon in possession of ammunition. In granting Knights's motion to suppress, the District Court held that, although the detective had "reasonable suspicion" to believe that Knights was involved with incendiary materials, the search was for "investigatory" rather than "probationary" purposes. The Ninth Circuit affirmed the statement. Three days after Knights was placed on probation, a Pacific Gas & Electric power transformer and adjacent Pacific Bell telecommunications vault near the Napa County Airport were pried open and set on fire, causing an estimated $1.5 million in damage. Brass padlocks had been removed and a gasoline accelerant had been used to ignite the fire. Suspicion for these acts had long been focused on Knights and his friend, Steven Simoneau. The incidents began after PG had filed a theft-of-services complaint against Knights and discontinued his electrical service for failure to pay his bill. Detective Todd Hancock of the Napa County Sheriff's Department had noticed that the acts of vandalism coincided with Knights's court appearance dates concerning the theft of PG's services. Then just a week before the arson, a sheriff's deputy had stopped Knights and Simoneau near a PG gas line and observed pipes and gasoline in Simoneau' ...