This chapter discusses the development and adoption of the mandatory Polar Code at the International Maritime Organization (IMO), and explores its relationship with the 1982 United Nations Convention on the Law of the Sea (UNCLOS) and various national regulations concerning shipping in the Arctic. It begins by summarising the legal regime for the Arctic region and reviewing the mandate of the IMO in general and under UNCLOS in particular. It then examines the efforts of the IMO to regulate shipping in the Arctic region, followed by discussion of the development of the Polar Code and the use of the tacit acceptance procedure to make it mandatory. The chapter continues to discuss the application of the Polar Code and the various challenges that states face in implementing the Code.