This paper aims at explaining why some developing countries adopt US-style IP rules that go beyond those required by the TRIPs agreement. It disentangles this puzzling situation in two manners. First, it explores one often neglected reason for the adoption of US-style rules, i.e. the socialization of decision-makers in the adopting country through interaction with experts in US IP law. Second, it relies on a more systematic conceptualization and measurement of variables than has been adopted in many previous studies. Overall, it brings forward strong quantitative evidence that socialization is a significant force in the export and import of IP rules.