Another Supreme Court case I’ve been following this fall is co-blogger Orin Kerr’s favorite, Carpenter v. United States. As folks will know from reading Orin’s blog posts or his superb amicus brief, the case asks whether it is a search for the government to obtain historical cell-site location data from your wireless provider. His most recent post, over at Lawfare, criticizes both Carpenter’s heavy reliance on the “mosaic theory” and some relatively arbitrary line-drawing required by that theory.

So I thought I would pop in to emphasize that there is an alternative theory that Carpenter has put forward, one that may avoid a lot of line-drawing problems and also has deep grounding in the history, structure and purpose of the Fourth Amendment. That theory is the Positive Law Model of the Fourth Amendment, which I wrote about (with my co-author James Stern) last year in the Harvard Law Review. (Our friend Richard Re has also put forward a related theory, the Positive Law Floor.)

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