Searches and seizures have long been held to be unreasonable under the Fourth Amendment unless supported by probable cause. Courts have only drawn a few narrow exceptions to that probable cause requirement. The Supreme Court found one such exception in the 1981 case of Michigan v. Summers, which gave police a limited authority to detain the occupants of premises that were lawfully being searched. The Court justified this limited detention by invoking the need for officers to have “unquestioned command” of the premises and prevent flight should incriminating evidence be found, thus “minimizing the risk of harm to the officers” and facilitating “the orderly completion of the search.” In 2005, police officers were preparing to execute a search warrant on a home in Wyandanch, New York, when they witnessed Chunon Bailey — who was unaware of the search warrant or its pending execution — exit the home and begin to drive away. Officers followed and subsequently stopped Bailey, detaining him about a mile from the premises to be searched. The government contends that Bailey’s detention was proper pursuant to Summers. The district court agreed and the U.S Court of Appeals for the Second Circuit affirmed, holding that the interests expounded in Summers justify the detention of a prior occupant of the premises to be searched so long as the detention is made “as soon as practicable” after identifying “an individual in the process of leaving the premises.” The Supreme Court agreed to review the case and Cato has now joined the ACLU and the New York Civil Liberties Union in filing an amicus brief urging the Court to reverse the Second Circuit. Our argument is three-fold. First, the Second Circuit’s extension of Summers lacks any limiting principles to the power to detain without probable cause. Without an outer limit, the Summers exception would be applicable to any number of situations in which detention without probable cause is unreasonable. A warrant to search a particular place would be transformed into a roving license to detain any person thought to be associated with that place. Second, the Second Circuit’s attempt to establish a limiting principle by requiring the detention to occur “as soon as practicable” is insufficient because it has no principled basis and is inconsistent with the underlying values of the Fourth Amendment. Furthermore, the “as soon as practicable” standard provides no clear guidance to officers as to when a detention is permissible. Finally, the extension of Summers here is unnecessary to ensure that officers maintain “unquestioned command” of the premises during a search: The detention of an individual away from the premises to be searched has nothing to do with police “command” of the premises, but is instead merely a means of holding someone pending the speculative emergence of probable cause.