The study of hard law and soft law in international environmental cooperation has mainly focused on why, and under what conditions, states choose one form of law in preference to another. This article develops an analytical framework for exploring the consequences of such choices. This framework is applied to implementation of international nutrient commitments in Norwegian agriculture from 1987 until 2007. Agriculture is the most important source of nitrogen inputs and eutrophication problems in the marine environment in Norway and Europe. It is concluded that, first, the consequences of hard and soft international law depend heavily on how they interact with changing national conditions. Some of these conditions can be deliberately changed to facilitate synergetic interaction between national conditions and international law. Secondly, under favorable conditions soft law can have a significant impact even when costly action is required, and resistance from target groups are strong. These observations are particularly interesting in light of the recent decision to end the soft law North Sea Conference process.