What is one main feature of Closed Registries?

One main feature of Closed Registries is that companies must be citizens of the state. In a closed registry system, only vessels that are owned by the nation's citizens can be registered, effectively limiting the ownership of registered vessels to those who hold citizenship. This requirement is established to promote national interests, protect local shipping industries, and ensure economic benefits remain within the country.

In contrast, other features such as allowing non-citizens to own vessels or permitting shipbuilding outside of the state do not align with the concept of a closed registry, which emphasizes local ownership and interests. Additionally, while crew requirements might vary in different types of registries, closed registries typically impose stricter regulations regarding crew nationality and certification to further support the national shipping agenda.