Mikel Garteiz-goxeaskoa, partner of AIYON Abogados S.L.P.
In recent years, the shipbuilding and energy industry has witnessed a profound transformation driven by the transition to sustainable energy sources. In this context, MORUs (Mobile Offshore Renewable Units) emerge as one of the key elements for the exploitation of renewable resources in the sea. These floating structures, designed to generate wind, solar, wave or tidal energy, represent a considerable technical advance, a challenge for the shipbuilding industry, but also, without doubt, a major legal challenge.
The Comité Maritime International (CMI), a non-governmental organisation in consultative status with the United Nations, has positioned itself as one of the main forums for the development of a uniform international legal framework for maritime affairs. Founded in 1897, the CMI’s main objective is the progressive harmonisation and unification of maritime law. In 2023, in view of the growth in the navigation of our seas by these new offshore structures, the CMI set up an international working group to study the legal status of MORUs and, in order to gather information on how these units are treated in different legal systems as part of this process, launched a questionnaire addressed to national maritime law associations.
The Spanish Maritime Law Association actively participated in this initiative, constituting a group of legal experts coordinated by Jose Sánchez-Fayos and myself. Its aim was to analyse the legal treatment of MORUs within the Spanish regulatory framework, the conclusions of which were presented at the Spanish Maritime Law Association National Congress held in Madrid in June 2025.
One of the central questions that arises when dealing with the MORU phenomenon is their legal status: are they legally ships or not? This is not a purely technical question as the answer will depend on whether or not essential maritime law regimes apply to them, such as the Convention on the Arrest of Ships, the LLMC maritime claims limitation regime, the rules on nationality and flag, maritime privileges or the possibility of being registered and mortgaged as a ship – essential for financing their construction. Ultimately, their legal qualification determines not only their administrative treatment, but also the legal architecture that guarantees their operation, financing, insurance and conflict resolution.
In the Spanish case, Law 14/2014 on Maritime Navigation establishes a typology of shipping vehicles that distinguishes between ships, vessels, naval artefacts and fixed installations. Most MORUs, not being self-propelled and not intended for navigation in the strict sense of the word, cannot be considered as ships. They do not easily qualify as vessels either. Thus, it can be concluded that most MORUs should be classified as naval craft, defined as floating structures not intended to sail, but capable of being towed and of accommodating persons or equipment.
This classification has important practical consequences as MORUs, identified as naval artefacts, can be entered in the Register – although this will require adjustment to accommodate them – and can benefit directly from the ship mortgage regime foreseen for ships. However, the 1999 Convention on Arrest of Ships does not apply to them, which prevents them from being arrested according to the procedures established for ships, something that we believe should be changed given the mobility of these artefacts.
On the other hand, as far as insurance is concerned, Article 406 of the Maritime Navigation Act admits the application of marine insurance to naval artefacts if they are subject to risks inherent to navigation, which opens the door to coverage during phases such as towing, installation or operation at sea.
Looking at the responses from other countries, France, for example, has recently passed the APER Law (2023), which explicitly excludes these structures from the concept of ship and creates a specific legal framework for them, recognising their stationary nature. Denmark, on the other hand, adopts a broader interpretation of the concept of ship, allowing MORUs to be registered as such in the Danish maritime register, which facilitates their insurance and financing. In the United States, the case law of the Supreme Court in Lozman v. City of Riviera Beach has set a standard by considering any structure that is reasonably capable of being used as a means of maritime transport to be a vessel, which has allowed some MORUs to be classified as such. In China, although the legal concept of ‘maritime mobile unit’ could be applied to MORUs, in practice there is still no possibility to register them as property in a public register. Brazil, on the other hand, allows their registration only if they are construed as vessels under the guidelines of the maritime authority.
As far as the registration aspects in Spain are concerned, it is noted that, for the time being, there is no specific framework in Spain that allows the registration of MORUs in the ship register of the Directorate General of the Merchant Navy as a category of its own, except by means of an analogue application. This is a major constraint that the DGMN should address as soon as possible so as not to prevent them from accessing financing through ship mortgages and using them as collateral in transactions. Furthermore, the absence of express recognition as ships limits their access to limited liability regimes, but not to the rights of innocent passage or transit through the sea, which are regulated by conventions such as the United Nations Convention on the Law of the Sea (UNCLOS).
The conclusions reached underline the need to adapt part of the Spanish -and in general, the international- legal framework to this new technological reality. It is proposed to review the registration regime and clarify its status in relation to liability, seizure and navigation rules. In short, the aim is to provide these units – essential for the energy transition – with the necessary legal security to operate effectively in international waters and in the exclusive economic zone of coastal states, as well as to ensure that there are no obstacles to their constructive financing, which is essential for their acceptance by the shipbuilding sector.
The emergence of MORUs is an opportunity for maritime law to evolve in step with technology. The work of the CMI and national contributions, such as in this case that of the Spanish Maritime Law Association group, constitute a fundamental first step in building a clear, predictable and future-proof legal framework for the sea.
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