This chapter sets out the theoretical framework—socio-technical systems theory—used in this book and the defence of the decision taken to use that framework from among the many alternatives available. It will explore the suitability of systems theory to address wicked problems. It will set out systems theory’s main concepts and see how they apply to organisations and socio-technical phenomena, using suitable models to address the research problem, the regulation of crypto-assets for the purposes of AML. This chapter will show the suitability of such an approach to AML and crypto-laundering. The chapter concludes with a brief discussion of alternative theories considered by the author for use in this book.