Today, the Cyberlaw Clinic filed a brief on behalf of the Electronic Frontier Foundation, defending the location privacy of the people of Massachusetts in the case of Commonwealth v. Rousseau. The Supreme Judicial Court had called for amicus briefs, asking the question of whether a passenger in a vehicle tracked by GPS had the legal right to challenge the collection of their location data. We argue that a passenger does have such standing, primarily because of the passenger’s reasonable expectation that their movements will not be tracked by the government without the issuance of a valid warrant. We also point out that courts must be vigilant in applying traditional legal safeguards against unreasonable searches and seizures in the context of increasingly invasive surveillance technologies.