Big data and advances in Artificial Intelligence, especially Machine Learning, have made it possible to do something which was unthinkable until recently, namely to tailor legal rules to the individual needs and preferences of different humans. This is the background to Omri Ben-Shahar’s and Ariel Porat’s ambitious and pathbreaking book, Personalized Law: Different Rules for Different People. Speed limits, standards of care in tort law, consumer protections, age restrictions for risky activity, and even voting rights could be personalized, according to the authors.

But should they be personalized? Ben-Shahar and Porat acknowledge that the personalized law project ‘is a massive undertaking that would radically change law and raise a plethora of challenges. Why do it?’ they correctly ask. Their answer is simple: ‘personalized law could better fulfill the goals of any system of rules.’ They call this the ‘precision benefit’ of personalized law.

In a recent Essay, I am asking the question: Why personalized law? I argue that this is a crucially important question and that Ben-Shahar’s and Porat’s answer to it is not convincing. The ‘precision benefit’ of personalized law is a distraction. The authors’ argument ducks the crucial normative issue of what inspires the personalized law project. The best justification for personalized law is utilitarian: maximizing social welfare. Hence, the personalized law project brings us back to an old debate about the role of economic analysis in lawmaking and adjudication: ‘Efficiency as a Legal Concern.’

But it would be wrong to conclude that it only offers us old wine in new bottles. Personalized law brings welfare maximization turbocharged by technology and administered by the state. The endpoint is not radical markets as some modern advocates of the economic analysis of law now propose. The endpoint would be a totalitarian dystopia. Confronting this prospect head on is necessary in order to see the fundamental problems of the personalized law project if executed uncompromisingly and radically. But it is also helpful to identify the limited legitimate uses to which personalized law can be put. I describe these, and I also explain why states should focus on regulating ‘wild’ personalization by powerful private actors instead of embarking on an ambitious personalized law program themselves.

Horst Eidenmueller is a statutory professor for commercial law at the University of Oxford.