National policy styles and path‐dependencies are inflicting on the abilities of Baltic Sea countries to deliver on their commitments under the Helsinki Convention. We here synthesize evidence and insights from studies relating to the provisions on agricultural nutrient management, a main source of marine pollution. We contend that governments that are strongly concentrated vertically, while fragmented horizontally, are lacking capacity, including with respect to informal institutions that can leverage implementation. As a stocktaking of institutional impediments to a sustainable development, the analysis has relevance to other international agreements where Baltic Sea countries are involved as key players. National policy styles and path‐dependencies are inflicting on the abilities of Baltic Sea countries to deliver on their commitments under the Helsinki Convention. We here synthesize evidence and insights from studies relating to the provisions on agricultural nutrient management, a main source of marine pollution. We contend that governments that are strongly concentrated vertically, while fragmentedhorizontally, are lacking capacity, including with respect to informal institutions that can leverage implementation. As a stocktaking of institutional impediments to a sustainable development, the analysis has relevance to other international agreements where Baltic Sea countries are involved as key players.