The notion that the risk problems confronting contemporary society are transscientific in character - that is, that while they can be posed to science, they cannot be-solved by science alone - has gained currency since Alvin Weinberg coined the term over thirty years ago. His prescription in such circumstances -that recourse must be had to legal procedures in order to find an answer - perhaps invests law with more ability than it actually possesses to deal with such issues, What is it about law that ensures that such problems are not also trans-legal? This article considers this question by examining the relationship between science and law, between the realms of the factual and of the normative, in order to determine what happens when the two come into-contact, or communicate, in the context of regulation or of litigation. Focusing on this crucial interface leads to the conclusion that traditional - formal and substantive - paradigms of law are ill adapted to cope with risk issues and that a procedural orientation of law is preferable. The question is then to choose among the leading alternatives available: Habermas's procedural paradigm based on the theory of communicative action or Teubner's reflexive law based, on-the theory of autopoiesis.