Environmental, social and economic capitals, capacities and carrying capacities provide the theoretical construct of the three dimensions of a sustainable development. Based thereon, this chapter aims firstly to provide a conceptual overview on two main objectives of multilevel rule of law systems that should be addressed when adapting these systems towards a more sustainable direction. This first aim is addressed based on ‘3-D Sustainability’, a concept offering six flexibly applicable decision-making criteria for priority setting between these sustainability dimensions based on the burden of proof in the sense of the precautionary principle. The theoretical application of these criteria on several real-world examples of legislative acts indicates the concept’s usefulness in practice. The two main objectives identified within this first aim are to stay through international environmental policy within the environmentally sustainable scale and to politically define flexible legal trade-off mechanisms, which more sustainably deal with conflicts among these sustainability dimensions. Secondly, the chapter strives to identify ways to strengthen the application of the existing international environmental legislation. Thus, several innovative mechanisms are identified that overcome current implementation and enforcement deadlocks, without changing existing laws, but also increasing its direct effect. In summary, the chapter innovatively offers—based on ongoing research—several solution proposals for addressing in a sustainable manner geopolitical and organizational scales as well as trade-offs when it comes to re-writing existing environmental legal institutions (de lege ferenda). It further provides proposals for the innovative implementation of existing normativeregimes without modifying legal text (de lege lata). © Springer International Publishing Switzerland 2016.