A new computer protocol, the Platform for Privacy Preferences (P3P), now allows for the automatic translation of World Wide Web (Web) sites’ privacy policies into an easily understandable form. In this Note, William McGeveran proposes a framework for lawmakers to take advantage of this new tool and respond to the threat to data privacy on the Web without unduly hindering the free flow of information. Like P3P’s strongest supporters, he perceives advantages in a “P3P privacy market” where individuals could use P3P to understand Web site operators’ privacy practices clearly, forcing below-par operators either to strengthen their policies or to offer visitors some benefit in exchange for personal data. While its libertarian proponents view this structure as a substitute for legal regulation, however, McGeveran argues that the regime should be predicated on contract rather than property principles and that law must play an active role in shaping and supervising the resulting market. He concludes by demonstrating how such a framework leaves lawmakers free to make a wide range of normative choices about privacy protection.