US Navy surface vessels, nuclear weapons, and the port visit problem

The USS Mesa Verde. Image: Ivan T/Wikimedia

I’m aware Ireland isn’t the only or even most interesting place where the practical implications of the Treaty on the Prohibition of Nuclear Weapons (TPNW) can be examined, but it is one. And I don’t see anyone else regularly writing about Irish anti-nuclear commitments: I see a niche, I fill it. So here we are again.

Ireland is notable among current state parties to the TPNW in that it is one of the most closely-aligned to the United States (and NATO), albeit at a distance in the military domain. Similar states include Austria, Malta, Thailand, New Zealand and the Philippines. That creates interesting issues, even under Ireland’s current policy of neutrality.

The USS Mesa Verde, a San Antonio-class landing platform, dock (LPD), visited Dublin Port on Friday August 25th and 26th, to coincide with the Notre Dame vs Navy American football game taking place that weekend. Such port visits by warships are a regular feature of international relations, and the US, with its large navy and network of international alliances and associations, is a frequent participant. But when warships visit states which are party to the TPNW, this poses interesting questions about the practical implementation of the treaty, particularly because of how incredibly cagey the US Navy (USN) is about nuclear weapons. I want to explore that here, with reference to the Mesa Verde but with an eye to the wider issue.

The Legal Aspect

Under Article 1 of the TPNW, each state party must “never under any circumstances…Allow any stationing, installation or deployment of any nuclear weapons or other nuclear explosive devices in its territory or at any place under its jurisdiction or control.”

Under Article 5, it is clarified that that each state must specifically “take all appropriate legal, administrative and other measures…to prevent and suppress any activity prohibited to a State Party under this Treaty undertaken by persons or on territory under its jurisdiction or control”.

In other words, it is not just that the Irish government may not possess nuclear weapons, but it has a positive obligation to “take all appropriate measures” to prevent the presence of nuclear weapons in Irish territory at any time. Allowing aircraft or ships carrying or armed with nuclear weapons to use Irish airspace or waters would be an abrogation of Ireland’s treaty obligations, and the government is required to take active steps, preventative and responsive, to stop this happening.

The Technical Aspect

According to publicly-available information, which for the US nuclear arsenal is quite good, the San Antonio-class cannot currently be armed with nuclear weapons. The ships were going to be fitted with the Mk-41 missile launcher, used by a variety of US and allied surface ships and capable of fielding a variety of missiles against naval, air and land targets. The latter role is mainly filled by the BGM-109 Tomahawk, a highly-versatile cruise missile. There did exist a version of the Tomahawk made to carry the W80-0 5-150kt nuclear warhead. That variant is understood to have been withdrawn from service in 2010, and a report from the Pantex nuclear weapons plant from 2012 appears to confirm that the last remaining W80-0s had been dismantled by then. As it happened, the Mk-41 was never fitted to the San Antonio-class anyway; little has been said about the planned armament since 2016, and it seems to still be in stasis.¹

For the USN, low-yield, sea-launched nuclear capabilities are currently only provided by Ohio-class ballistic missile submarines using one of the variants of the Trident missile. The Trump administration had planned to develop a new sea-launched nuclear cruise missile (SLCM-N), but Biden killed the project. Congressional Republicans as well as chunks of the national security establishment continue to push for the programme’s restart, so depending on the outcome of the 2024 election, the SLCM-N (and with it, the nuclear capability of the USN’s surface fleet) could yet rise from the grave.

This does not necessarily preclude an LPD (or any other non-Ohio-class ship) from carrying nuclear weapons—exactly how nuclear weapons are usually transported by the US military is, unsurprisingly, rather an opaque subject, but sea transport is certainly an allowed mode—but it does make the likelihood of nuclear weapons being on any particular LPD at any given time very low.

¹ Thanks to my good friend Louis Martin-Vézian for tipping me off about this, I was using outdated info.

The Declaratory Aspect

The real problem arises from US Navy (USN) policy. In late 1991, with the Cold War winding down, then-President George H.W. Bush instructed the USN to begin removing all nuclear weapons from surface ships and attack submarines. The process was completed by mid-1992, leaving the Ohio-class the USN’s platform for nuclear weapons, with its high-yield Trident ballistic missiles, and low-yield Tridents and Tomahawks (until the latter were retired in 2010, as discussed above). This meant that in 1996, the commander of the USS John F. Kennedy was able to confirm to the Irish Times that the ship carried no nuclear weapons when it visited Dublin that year. I have not been able to confirm that those assurances were given in response to an Irish government request, but given the TPNW would not be ratified for another 24 years, there existed no domestic or international legal obligation to do so then. In either case, the confirmation was likely politically important, given longstanding anti-nuclear sentiment in Ireland.

However, in 2006, the USN’s Chief of Naval Operations issued a directive entitled “Release of Information on Nuclear Weapons and on Nuclear Capabilities of U.S. Forces”. Among other things, it stipulated that:

“Military members and civilian employees of the Department of the Navy shall not reveal, purport to reveal, or cause to be revealed any information, rumor, or speculation with respect to the presence or absence of nuclear weapons or components on board any specific ship, station or aircraft, either on their own initiative or in response, direct or indirect, to any inquiry.”

Release of Information on Nuclear Weapons and on Nuclear Capabilities of U.S. Forces, US Department of the Navy, 2006

This policy, usually referred to as Neither Confirm Nor Deny (NCND), remains in effect, as far as I know. The Congressional Research Service referred to it as current policy as of 2021, and doubtless someone would have noticed if a retraction had been issued within the last two years. It is not difficult to foresee the clash between the USN’s refusal to comment on the presence/absence of nuclear weapons on its vessels, and the positive obligation on TPNW states to ensure no nuclear weapons enter their territory.

There is precedent for navigating this issue. New Zealand is a TPNW state party, but more than that, has since 1987 maintained a prohibition in domestic law on the entry of nuclear-powered ships or ships carrying nuclear weapons into the country’s territorial waters. After the passage of the legislation, no USN vessel visited New Zealand for 29 years. This changed in 2016, when the Arleigh Burke-class destroyer USS Sampson visited, and indeed aided in relief efforts after the 2016 Kaikōura earthquake.

The NZ situation is subtly distinct; the complete absence of USN ships from the country’s waters for three decades was mostly US policy, signalling objection to the nuclear-free zone (and featuring a reciprocal ban on NZ ships visiting the US, until 2014) . The change in 2016 was widely seen as final US “acceptance” of NZ’s position, but did not see any abrogation or suspension of the NCND rule. The NZ anti-nuclear legislation merely requires the prime minister to be “satisfied that the warships will not be carrying any nuclear explosive device upon their entry into the internal waters of New Zealand” in order to grant access. Wellington made an assessment based on publicly-available information about the capabilities of the Arleigh Burke-class and achieved the necessary satisfaction on the prime minister’s part that the Sampson was not nuclear armed. The TPNW was not a factor, as it was not signed until 2017.

Treaty obligations and signalling

The question then is, what level of certainty must TPNW state parties achieve that a vessel is not nuclear armed before granting it access to their territorial waters, and can this level of certainty be achieved for USN vessels given the NCND policy.

The answer is up for debate. One could argue that the NZ solution is fine; that in practice the chances of any US warship other than a ballistic missile submarine carrying nuclear weapons at any given time are extremely low, and thus port visits by such ships present no problems to TPNW state parties. On the other hand, the language used in the TPNW is arguably quite a bit stronger than the NZ legislation, specifically requiring “all appropriate legal, administrative and other measures…to prevent and suppress any activity” rather than merely that “the Prime Minister shall have regard to all relevant information and advice” until they are “satisfied that the warships will not be carrying any nuclear explosive device.” To me, this appears to confer a stronger preventative obligation, and state parties should take a stronger stance than NZ did in 2016.

As is so often the case with international law, the fundamental issue is much more political than it is legal. The TPNW has only been ratified by states with existing antipathy towards nuclear weapons; the point is much less to have enforceable bans on such weapons, and much more to contribute to creating a strong international norm on the barbarity and odiousness of such weapons, hopefully laying the groundwork for future arms control and disarmament efforts with nuclear-armed states. It’s about signalling.

The NCND policy is in part a security measure; ambiguity about where nuclear weapons are or are likely to be is a good way to prevent an adversary from attempting to attack or steal them in transit. But it is also, like the TPNW, a political statement. By refusing to provide even confirmation of the absence of weapons, the USN is asserting impunity from international scrutiny and a right to carry such weapons wherever and whenever it pleases, despite the transnational threat they pose to human life and security, and despite the right of states to adopt prohibitions on the presence of nuclear weapons. Such a statement runs directly counter to the principles of the TPNW, the signalling it is meant to achieve, and the stated desire of countries like Ireland to reinforce a taboo on nuclear weapons.

In my view, therefore, TPNW state parties should push back against such policies. They should take seriously their obligations to actively prevent transit of nuclear weapons through their territory and demand confirmation that aircraft and ships are not carrying them. Mere assessments of low likelihood, like NZ in 2016, are not enough. If they do not receive confirmation, they should deny entry. This should be policy and, ideally, be codified in domestic law.

For the purposes of this article, I submitted a query to the Press Office of the Department of Foreign Affairs, asking if it or any other part of the Irish government had sought or received assurances about the absence of nuclear weapons aboard the Mesa Verde during its visit to Dublin, referencing the state’s TPNW obligations as I did so, but did not receive a response. I do not know, therefore, if they asked, or even carried some kind of formal external assessment of the Mesa Verde’s capabilities à la Wellington in 2016.

It is good at least that the DFA claims it is policy to confirm all aircraft transiting Irish airspace are unarmed, but in practice, the government receives only cursory details of overflights after the fact in the case of the US. Shannon Watch has also noted that the government grants hundreds of exceptions per year to the “unarmed” requirement, and I can find no information anywhere on whether it is policy to specifically enquire about nuclear arms.²

That’s not really good enough. Ireland has, as I have discussed previously, a strong history of anti-nuclear advocacy, and moments like this are great opportunities to do more. We should not be afraid to stand up to the US in frankly quite small ways to do so; if we are serious about achieving a nuclear-free world, we are at some point going to have to tell the Americans off, to their faces.

At a certain point this begins to merge with my broader discomfort about Ireland’s deference to the United States, of which the over-the-top celebrations around the Notre Dame-Navy game are a potent symbol. I would like to be part of a nation with a stronger moral backbone.

This issue applies more widely than just in Ireland, though; it is about when TPNW state parties must take their obligations seriously. The US-aligned countries mentioned at the beginning, like the Philippines, must think about what commitment to disarmament really means; NZ, for example, must consider acting more forcefully in future than it did in 2016.

The principle applies to port visits and overflights from non-US nuclear states too, though few of them move their nuclear weapons around the world and deploy them on a variety of platforms in the way the US does. Achieving confirmation of aircraft and ships’ non-nuclear status should therefore be easier, but it is just as important to seek it; the point is, as discussed previously, to make a point.

The TPNW is about signalling, but if the treaty remains merely a piece of paper, that signalling will be weak; it must have on-the-ground implications, and the Irish government must understand that some of that ground is in Dublin Port.

² At some point I may try FOI-ing this, but given the widespread practice in the Irish public sector of denying FOI requests or heavily redacting released documents, and given this is even vaguely related to an issue of security, I am not at all hopeful.