Kiel Robert Brennan-Marquez

The Constitutional Limits of Private Surveillance

The age of data-driven law enforcement is upon us. As a consequence, government officials now rely heavily on private surveillance technology to forecast threats, drive investigation, and mobilize enforcement. On the whole, this development is welcome; the use of privately-collected data promises to refine policing and counterterrorism efforts. But it also has major implications for constitutional privacy. For the Fourth Amendment to safeguard privacy into the future, its approach to state action must change. Instead of turning, as it has historically, on the extent of government influence over private surveillance activity, the Fourth Amendment’s coverage should depend on whether private surveillance activity effects an extension, in practice, of law enforcement’s infrastructural capacity. In addition to its normative benefits, the “infrastructural” approach also resolves certain mysteries within existing law and brings the Fourth Amendment into greater alignment with broader patterns of state action jurisprudence. Most importantly, focusing on infrastructure underscores the connection — unappreciated to date — between (1) law enforcement’s compulsory seizure of privately-held data, enabled by the so-called “third-party doctrine,” and (2) informal data-sharing between law enforcement and the private sector. The third-party doctrine is teed up for reform this term in Carpenter v. United States. But no such progress is on the horizon for informal data-sharing. Doctrinally, the issues have been compartmentalized, even though, at an infrastructural level, they represent two sides of the same coin. Both are mechanisms by which law enforcement officials capitalize on private surveillance technology in lieu of performing surveillance directly — and both thus facilitate bulk, warrant-less data collection by the state. As such, a full solution to the shortcomings of the third-party doctrine demands parallel attention to the shortcomings of the Fourth Amendment’s antiquated state action rules, and vice versa. Solving one problem in isolation from the other risks a partial victory — or even a Pyrrhic one, to the extent that reform of the third-party doctrine could encourage even more informal data-sharing between the government and the private sector. Against this backdrop, the infrastructural approach offers an integrated path forward, and one that will only become more urgent, over time, as data-driven law enforcement practices intensify.