During the course of commercial activities involving ships, many legal questions will arise which, if unresolved, may grow into problems that need a solution before they incur liability for the shipowner and seafarer. Such issues will be managed by the parties and their advisers as part of their day-to-day business, without any wish to get involved in litigation, but the laws which define the systems in the Flag State must be applied wherever the ship may be in the world, while the Port State laws must be applied in their sovereign jurisdiction. The relationship between international law and domestic law is the foundation upon which maritime law must stand and, in this chapter, we are introduced to maritime law and management with a foundation of legal theory and how that is put into practice. We shall see where it all starts, with Sources of Law, and the structure of the Sovereign State, which we must then place in the context of international shipping, with the international law of the sea.