This dissertation evaluates the role and effectiveness of law in the transboundary environmental governance of the Baltic Sea with regard to eutrophication. To this end, it reviews the applicable international agreements with their related instruments, as well as the EU legal frameworks, for the protection of the Baltic Sea environment on the basis of theories on resilience in social-ecological systems. The scientific discourse on resilience in social-ecological systems provides theories on effective governance of complex environmental problems with nonlinear causal connections. The governance features identified in resilience governance also show significant similarities with characteristic features of the concept of ecosystem approach. The resilience features can thus provide guidance to the operationalization of this concept, which lacks a distinct meaning in the legal context.

Eutrophication is one of the main environmental problems in the Baltic Sea. Despite the fact that this problem has been acknowledged since the 1970s, only little progress has been visible in the attempts to limit the problem. Environmental governance in the form of cooperation and common action has, however, been established by the coastal states of the Baltic Sea to reduce the discharges to their common resource. This was originally coordinated through the Helsinki Convention and its administrative organization HELCOM in the 1970s. Since the year 2000 a new set of legal instruments and approaches have developed, emphasizing also the ecosystem approach. These instruments have a basis both in HELCOM and in EU environmental law, most significantly represented by the Water Framework Directive and the Marine Strategy Framework Directive. They establish a unique regulatory structure, with new approaches to regulation, which also give rise to questions regarding interpretation and effectiveness that have not previously been analyzed.

It is concluded that applicable law in the Baltic Sea area reflects resilience features such as adaptability, flexibility and redundancy within the legal structure. The legal structure for the Baltic Sea is dynamic and stretches over many levels of governance. The applicable legal instruments are constructed so as to be adaptable and flexible. The legal instruments moreover include significant elements that provide for participation at different levels and in different forms, which contribute to enabling the mentioned resilience features. However, the Baltic Sea legal structure – as law in general – has different core functions than just providing for effective environmental governance. Law is based in a number of general principles connected to the rule of law and the function of law as a foundation for stability in the society and in human interactions. These principles are also important since they are directly linked to enforcement, monitoring and control. While the legal structure in the Baltic Sea may provide for effective governance and social-ecological resilience, the resilience features reflected in law do not always appear as far-reaching as suggested by resilience theories, much due to the legal principles. It is however because of these principles and the base for binding requirements they enable, that law can push for governance measures and features that might not have been accomplished otherwise. This, in the larger perspective, includes creating requirements that steer human activities away from critical thresholds.