Should we allow for “efficient breach” in international law? That is one of the questions that Professor Joost Pauwelyn poses in Optimal Protection of International Law. If this question were asked by anyone named Posner, either Richard or Eric, or any of their fellow travelers, European international lawyers would shake their heads at American frivolity and even folly. They would wonder why so many Americans continue playing around with economic models of rules and contracts when the fragile edifice of international rules safeguarding the peace, health and welfare of the planet needs all the strengthening it can get. From their point of view, the optimal level of protection is clearly the strongest level of protection. American partisans of law and economics, on the other hand, would assume that the optimal level of protection is the level that allows for the greatest freedom of action. The actual knowledge or thinking of neither side would be advanced.

But Professor Pauwelyn is not an American international lawyer, or at least not of the traditional kind. He has taught at a leading American law school, but he is Belgian by birth, educated in Belgium, England and Switzerland, and a veteran of the legal affairs division of the World Trade Organization. He is thus deeply familiar with European approaches to international law and writes with a keen awareness of the standard transatlantic dichotomy between legal formalists and legal realists.