The legal basis for the nationality of seagoing vessels can be found in article 91 of the Law of the Sea Convention (LOSC). This article determines that “Every State shall fix the conditions for the grant of its nationality to ships, for the registration of ships in its territory, and for the right to fly its flag. Ships have the nationality of the State whose flag they are entitled to fly. There must exist a genuine link between the State and the ship.

In addition, article 94 LOSC sets out what the duties of the flag state are. In general it comprises that the flag state must effectively exercise its jurisdiction and control in administrative, technical and social matters over ships flying its flag.

In the Netherlands seagoing vessels are regarded as registered property which means that ownership and rights established over the vessel such as mortgage need to be registered in the registry for registered property with the Kadaster. In the past registration with the Kadaster meant that the vessel also obtained Dutch nationality. As a consequence a Dutch registered vessel, for instance for the establishment of a Dutch mortgage, could not be operated outside of the Netherlands. If a Dutch owner wanted to operate a vessel from outside of the Netherlands ownership needed to be transferred to a foreign entity as well. The only exception to this being if the vessel was under bareboat charter as there was a possibility created to make use of the so-called bareboat registry (bareboat- in as well as bareboat-out).

After a long legislative progress starting back in 2011 the system has now been changed with the coming into force of the new Rijkswet Nationaliteit Zeeschepen (RNZ) as of 1 July 2025. Where vessel owners in the past needed to apply for a declaration of nationality with the Dutch Ministry for Infrastructure before they could register ownership of the vessel, they now need to register ownership first after which they can apply for Dutch flag registry and Dutch nationality of the vessel (or opt for another registry).

The conditions for the registration in the flag registry are stated in articles 6 and 7 RNZ. As soon as registration in the flag register is completed the Certificate of Registry is issued. These conditions include that the vessel and operation of the vessel comply with all the applicable regulations with regard to safety and navigation of sea going vessels, crew and other passengers and with regulation in respect of the prevention of pollution.

The RNZ however does allow the crew management and employment of the crew to take place outside of the flag state as long as an administration is kept in the flag state of all the crew members on board, their qualifications and duties and of the employment contracts.

The separation of ownership and nationality also means that it is now also will be possible to withdraw nationality of the vessel under certain circumstances as a sanction. This was not possible in the past. In article 13 the conditions and procedure for withdrawal of the flag state registration are set out. The Minister can for instance withdraw the flag state registration in case a vessel was involved or if there are serious grounds for suspicion of involvement with piracy, human trafficking, illegal broadcasting, drugs and weapon trafficking or terrorist activities, but also the illegal transport of illegal immigrants is mentioned. This means that under the RNZ it may be possible to ban organizations such as Sea-Watch, active in the Mediterranean Sea and known for rescue operations of immigrants, from flying the Dutch flag.

The RNZ also provides a legal basis for the bareboat registration (article 9) which previously was not in place.

Finally, the RNZ not only applies to the Netherland but to all countries within the Kingdom of the Netherlands (Aruba, Curaçao and Sint Maarten) and the special municipalities within the Kingdom (Bonaire, Sint Eustatius, Saba) making sure a uniform procedure applies for all vessel registrations in each country within the Kingdom of the Netherlands where previously separate laws were applicable for each country of the Kingdom.

Whether the RNZ and the new procedure for flag state registration indeed will provide more efficiency of course remains to be seen. The fact that we are now dealing with one law only is already a mayor improvement. It will also be interesting to monitor if and when the Minster will make use of the possibility to withdraw flag state registration and whether these withdrawals will then be opposed; this are undiscovered territories of maritime law.