This chapter provides the necessary background as to why addressing the issue of the rights and obligations of States prior to delimitation is both pressing and topical. The main objective of the book is to lay out the rights and obligations of States (i.e. claimants and third States) under international law in disputed maritime areas. Particular emphasis in this regard is placed on those areas where States have not agreed upon delimitation (a), neither have been able to agree on cooperative arrangements (b), and for which a modus vivendi has not been developed to regulate activities in a disputed maritime area (c). Apart from that, States are obligated to take certain (unilateral) measures in disputed areas. This is because entitlements to maritime zones come with related obligations for the coastal State regarding certain issues. For instance, with regard to managing and conserving living marine resources, as well as protecting the marine environment, coastal States have significant obligations under the LOSC. Another issue that is discussed is how jurisdictional uncertainty, which is inherent to disputed maritime areas, affects claimant States, third States and their nationals.