This thesis focuses on a case study of the Natural Park of the Coral Sea, a large marine protected area (LMPA) created in New Caledonia, to understand changes in governance of the Exclusive Economic Zone (EEZ). While the ocean sector is booming due to the blue growth discourse and new technologies are enabling humans to access resources previously inaccessible, the global ocean is facing a multidimensional governance crisis. This crisis is enhanced in situations where sovereignty is contested. Large marine protected areas are an excellent proxy to study changing global governance arrangements over Exclusive Economic Zones and the enduring place of the state as the predominant actor in international relations. The question of who governs the ocean is an extension of treating ocean space as land space through territorialisation processes to secure resources. States, subnational state actors (including subnational island jurisdictions), and nonstate actors are increasingly treating oceans as land through territorialisation processes to secure resources. Large marine protected areas have emerged in response, but are controversial and have been seen as geostrategic tools rather than conservation instruments. Studies of LMPAs to date have focused on the disproportionate influence of large charities and have warned such projects could lead states to relegate part of their decision (Mallin et al. 2019; Silver and Campbell 2018). The influence of large charities has been very controversial and led some to suggest sovereignty and authority might be slipping out of the hands of states; however, I found this not to be the case in New Caledonia. Through my analysis of the Natural Park of the Coral Sea, I mapped the different groups of actors (state, sub-national states, and nonstate) involved in the governance arrangements and found that government actors (both from the French state and the New Caledonia/Kanaky government) had the upper hand in the decision-making in a governance arrangement meant to be consensus-based. Conventional International Relations (IR) treats the Westphalian state as a unitary actor and would therefore consider France as the state and New Caledonia/Kanaky only as the subordinate entity (considering it is a French overseas territory). By using an actor-centric institutional approach rooted in polycentricity and the ‘global governors’ model of Avant and others (2010), I demonstrate that while states are still the primary actors in governance, looking at the state solely as a unitary actor obscures the agency of polities such as sub-national island jurisdictions. I find New Caledonia/Kanaky has established control over its Exclusive Economic Zone (EEZ) through the creation of the Natural Park of the Coral Sea, but France retains the sovereign power to influence or block legislation. Ultimately, states (including subnational state actors) have retained power over LMPAs and, as such, they are political objects as much as conservation projects. However, LMPAs also represent an opportunity for subnational entities to exercise power. Concerning global governance arrangements, I uncover additional findings related to the role of science and NGOs in relation to LMPAs. Expertise and advocacy are often working together in marine conservation, steering towards area-based targets and large marine protected areas. Expertise seeks complex governance arrangements to try and create authority for themselves. Additionally, the intertwining of expertise and advocacy can lead to path dependency to the potential detriment of alternative tools of conservation. I concur with previous works which warn that LMPAs can be geostrategic tools rather than protection instruments, but my findings temper this, recognising that they can still have protection value.