The objective of this chapter is to give insight in marine governance challenges, illustrated by Arctic shipping. To do this, this chapter presents a theory of marine governance as reflexive institutionalization, in which the structural properties of marine governance arrangements are (re)produced in interactions between governmental actors, maritime sectors and civil society actors within the structural conditions of the networked polity at sea. Based on an analysis of the institutionalization of shipping governance arrangements of three (possible) Arctic shipping routes; The Northwest Passage (NWP), the Northeast Passage and Northern Sea Route (NEP/NSR), and the Transpolar Sea Route (TSR) the following question will be answered, “What are the enabling and constraining conditions of marine governance as reflexive institutionalization?” In other words, what are the possibilities for public and private actors to challenge discursive spaces and to change the rules of the game, in order to find solutions for environmental, spatial, economic, and social problems at the Arctic Ocean? The analysis shows forms of institutionalization as structural reflectiveness in which the dominant discourse ‘shipping is allowed in the Arctic’ is not challenged. However, this form of reflectiveness showed how actors, such as China and Russia, are able the use rules from different institutional settings to strengthen their position.