Un-crewed vessels and the definition of a warship under UNCLOS Article 29: Question 6)
“…a ship belonging to the armed forces of a State bearing the external marks distinguishing such ships of its nationality, under the command of an officer duly commissioned by the government of the State and whose name appears in the appropriate service list or its equivalent, and manned by a crew which is under regular armed forces discipline”.
The importance of “warship” status
8. In addition to the above, all vessels or ships have the right to certain passage rights, such as transit passage through international straits and innocent passage in territorial seas of another State. Whilst not dependent on warship status, it is important to highlight as it is a right we would wish our un-crewed vessels to be able to assert.
9. Un-crewed vessels currently being trialled within the RN are registered as government vessels on non-commercial service, affording them the ability to assert the rights of both sovereign immunity and passage. However, so far, these vessels are either not designed to be operated belligerently or are still considered to be “experimental” rather than at the stage of being commissioned into Service.
10. As systems mature, it will be necessary for the UK to settle the status it asserts for un-crewed vessels. There is not yet international consensus on the issue, though many states are developing un-crewed vessels for military purposes. The MOD considers that the key principle to uphold is that of distinction – in order that the operation of un-crewed vessels during Armed Conflict should not increase the risk to non-combatants. While UNCLOS does not deal directly with the issue of distinction, the purpose behind Article 29 is to attach state responsibility to the activities of a ‘vessel’ capable of acting in a belligerent manner, and allow non-belligerents to understand the extent of lawful conduct by vessels of different types. Further, this ensures that the effects of warfare are limited to only legitimate targets.
11. To balance this requirement for warships to act responsibly, through the principle of sovereign immunity, UNCLOS limits the controls that coastal states may assert against the peaceful use of the sea by the warships of another state – this measure is designed to reduce tension and the risk of misunderstanding between states – and to prevent the improper extension of the authority of states beyond their own borders.
12. UNCLOS therefore uses Article 29 to confirm state responsibility for the actions of warships and requires that the state have an accountable system of discipline to control the actions of those who operate them. Un-crewed vessels should be incorporated into this regime to regulate their proper use. This would be best achieved by an acceptance that Article 29 applies to state operated military un-crewed vessels (i.e. those which are intended to make a direct contribution to a military effect).
13. Some states might seek to avoid the control which flows from Article 29 by arguing that because the ‘crew’ are not embarked, the un-crewed vessel is in fact a military device rather than a vessel. Should this be the case, then Additional Protocol 1 to the Geneva Conventions would be engaged, and state responsibility would attach to the decision to deploy the device as a “means or method of warfare”. But those ‘devices’ would not be entitled to the privileges of a warship (or any flagged vessel) as regards third states – and so would be liable to seizure and enforcement actions if they entered the territorial sea of another state. Further, as ‘devices’ they would not be able to assert the passage rights afforded to all vessels.
14. The MOD position is that the matched authorities and safeguards which flow from Article 29 are suitable for military un-crewed vessels and should be applied to them.
15. Opponents to the MOD position may argue that at the time of the UNCLOS III negotiations, the Conference did not consider un-crewed vessels because of the technology available at the time.
16. The MOD’s position is that this does not mean the Convention is not capable of application to new technology. Case law post the ratification of UNCLOS has established that the Treaty can be interpreted in the light of new technology rather than ignoring it.
17. Noting that Article 29 also stipulates that a warship must also bear “the external marks distinguishing such ships of its nationality”, the MOD considers that this also applies to un-crewed vessels. Thus, an un-crewed vessel which has been declared as a warship of the Royal Navy would both have a pennant number and fly the white ensign.
18. The MOD therefore considers UNCLOS is ‘fit for purpose’ in the 21st Century – provided the interpretation suggested above is adopted. By declaring an un-crewed vessel as a warship, the UK is making a formal assertion of responsibility, authority and immunity. The same responsible course should be taken by other operating states.
Received 11 November 2021
 UNCLOS Articles 19, 38, 52, 53.
 For example, with reference to the application of new technology to the principles of hot pursuit under UNCLOS Article 111, see Arctic Sunrise Arbitration para 259-260.