In this first SoLaR working paper we are reviewing the literature on EU soft law, with a special focus on research dealing with competition law, state aid, financial regulation, environmental protection and social policy. The literature reviewed consists of studies conducted at the EU level of governance. A further paper will focus on nationally centered analyses, in particular concerning Finland, France, Germany, Italy, the Netherlands, Slovenia, and the UK. The present paper first discusses different definitions of soft law and taxonomies before moving to an analysis of status and legal effects of soft law. The paper then reviews studies dealing with the interface between soft law and adjudication. It finally looks into issues concerning the justiciability of soft law instruments in order to distill a theory with regards to the use of soft law in courts and national administrations. The paper concludes by looking at the consequences that the enforcement of soft law can have from a rule of law perspective.