This chapter discusses the role of soft law in international law, in particular in the field of sustainable development law. Soft law is often regarded as nonlaw. However, this qualification increasingly does not match the realities of the development of international law in which many legally relevant statements are made in the form of soft law, while many so-called hard law obligations are rather soft. A comparison between the Sustainable Development Goals (SDGs) and the Paris Agreement on climate change, both adopted in the second half of 2015, is used to illustrate these points. It is argued that the development of international law can be better understood by placing legal statements on a continuum from weak to strong legal pronunciations instead of using the binary approach that distinguishes between hard and soft law and that qualifies soft law as nonlaw.