The Law of Armed Conflict, the Law of Naval Warfare, and a PRC blockade of Taiwan

In discussions of possible Peoples Republic of China (PRC) military courses of action against Taiwan that rise to the level of an armed conflict, the likelihood of a PRC naval and air “blockade” is often considered. The Republic of China (ROC) Foreign Ministry noted in November 2021 that,

At present, the PLA is capable of performing local joint blockade against our critical harbours, airports, and outbound flight routes, to cut off our air and sea lines of communication and impact the flow of our military supplies and logistic resources….

Indeed, in response to a visit by US Speaker of the House, Rep. Nancy Pelosi to Taiwan in August 2022, PRC forces essentially rehearsed how to do this. However, from law of armed conflict (LOAC) and law of naval warfare (LoNW) perspectives, the implications that might follow from either a declared or tacit PRC blockade of Taiwan are actually as legally complicated as they are practically significant.

This is not least because of Taiwan’s legally challenging status in that it is not, according to the PRC which effectively considers Taiwan a rebel province, a sovereign “State” (including for LOAC characterization purposes). Nor is this status challenge merely a function of, and thus limited to, a bespoke PRC interpretation. It also holds for many other States, noting their “one China” policies. This includes many of the potential third State combatant parties that might be drawn into such a conflict, such as the United States (as indicated at both political and military levels), Japan, and Australia.

A NIAC “Blockade?”

Should an armed conflict take place, can there even be a LoNW blockade? The logical, legal consequence of the PRC’s view of Taiwan as a rebel province is that the PRC’s initial characterization of an armed conflict with Taiwan would necessarily be that it is a non-international armed conflict (NIAC); it could not be an IAC as Taiwan is not, according to the PRC, a “State.”

This is significant because “blockade,” as a LoNW method of warfare, is irrelevant to NIACs (except, as dealt with below, in the situation of a formal recognition of belligerency). There are many reasons for this de jure non-availability including: that the law of blockade is a scheme for regulating relations between combatant State belligerent naval operations and neutral State vessels; that there is no neutrality status in a NIAC; and that blockades can operate in the high seas, whereas NIAC operations cannot (or rather, at law, generally should not) interfere with other States’ vessels beyond the national waters of the conflicted State.

So, at the early stage of a PRC-Taiwan armed conflict, the PRC – if it wants to implement a blockade – really only has two options, and each carries with it quite significant legal implications.

Option 1: A Policing Operation Limited to the Territorial Sea

The first PRC option is to avoid all reference to a LoNW blockade and to describe its maritime interdiction regime as merely a function of maritime policing around a rebel province. This is permissible in Law of the Sea (for example, through temporary suspension of innocent passage for security reasons in a part of the “PRC territorial sea” (UN Law of the Sea Convention (LOSC) art. 25(3)). Nor is there any rule in NIAC LOAC that prohibits such action, so long as it does not extend beyond the territorial sea. Indeed, there is State practice that points to the permissibility of such action (for example, during the Sri Lankan NIAC against the Liberation Tigers of Tamil Eelam). This form of interdiction operation was accepted by (for example) the United Kingdom as legitimate during the civil war between the PRC and Taiwan in the late 1940s and into the early 1950s.

But the consequence of this approach is that the PRC cannot lawfully extend any of its blockade-like interdiction measures beyond the territorial sea. That is, the interdiction operation would not be lawful in that rather substantial part of the Taiwan Strait that is outside the PRC territorial sea as understood in orthodox law of the sea terms. If the PRC did seek to impose these measures beyond the territorial sea, then this brings with it two further legal options. The first would be to declare that the PRC is in clear breach of international law in interfering with other States’ vessels on the “high seas” (which for these navigation and overflight purposes includes the EEZ outside of territorial seas – LOSC art 58). France did something similar during the Algerian War, never making clear what the legal basis for these high seas interdictions was, and their actions were (rightly) condemned as not compliant with the applicable international law.

Option 2: Formally or Tacitly Recognise Taiwan’s Belligerency through a LoNW IAC Blockade

The other legal option that could flow from a PRC implementation of a (LoNW) “blockade” is that the law applicable to the conflict would become, de jure, IAC LOAC. This outcome is only permissible in a NIAC situation (which the PRC will obviously want to call the conflict, in order to maintain their broader position on the legal status of Taiwan) where either: (1) the situation envisaged in article 1(4) of 1977 Additional Protocol I exists (unlikely in this particular case); or (2) there is a formal recognition of the belligerency of the rebel entity (Taiwan) by the combatant State (PRC). In such recognition of belligerency situations, the applicable LOAC ruleset then becomes the IAC rules, rather than the NIAC rules.

This outcome regarding the applicable LOAC both indicates and follows from the fact that a customary attribute of the doctrine of recognition of belligerency is that the declaration of a blockade by the combatant State in relation to the rebel entity in fact operates as tacit recognition of that rebel entity’s formal belligerency. This was the case—which the United Kingdom and ultimately the United States accepted—during the US Civil War, for example, where the United Kingdom characterized the Union’s declaration of a blockade on the South as a tacit recognition of Confederate belligerency. Such an act then brings with it the de jure application of IAC LOAC (including the permissibility of blockade). But it is important to recall that once the IAC LOAC rules come into play, all of those rules come into play, including the status of neutrality for any (other) State that recognizes either the blockade or the rebel entity’s formal belligerency. And with neutrality comes a range of oft-forgotten, but really significant powers and obligations, including powers to deal with belligerent shipping and personnel in neutral ports.

Other (Third) States?

However, regardless of what legal justification the PRC promotes (if any – they may choose opaque silence, as France did with respect to the high seas interdictions during the Algerian conflict), a third State (the United States, for example) may at any rate wish to recognize Taiwanese belligerency early in the conflict. This is entirely permissible if the requirements for this recognition are met. These include (as set out in a 1956 UK legal opinion): there is underway “an armed conflict of a general (as distinguished from a purely local) character;” the “rebel” group “must occupy and administer a substantial portion of the national territory;” the “rebel” group must “conduct the hostilities in accordance with the rules of war and through organised armed forces acting under a responsible authority;” and there exist “circumstances which make it necessary for outside states to define their attitude by means of recognition of belligerency” – such as the desire to impose (PRC), or respond to (other States) a “declared” blockade.

A third State may therefore wish to recognize Taiwanese belligerency for a range of reasons, including the ability to assert the application of IAC LOAC as between the combatant State and the “rebel province.” Such recognition would in turn provide scope to hold the PRC to account as against the IAC LOAC ruleset. However, where a third State does recognize a rebel entity’s formal belligerency, then that State will rightly be subject to both a legal obligation, as well as international pressure, to regularize its own relations with the contending parties.

One option for that third State is to declare its neutrality. In that case it must order its own merchant vessels to submit to any PRC or Taiwanese visit and search regime, or comply with any PRC or Taiwan imposed blockade. Another option available to third States – noting existing political expressions of intent – is to intervene on the side of Taiwan, which then creates an IAC between the PRC and that (those) intervening State(s), which will co-exist in the same battlespace alongside the recognition of belligerency-based conflict between PRC and Taiwan.

Conclusion

It is possible, indeed likely, that in any blockade-like action designed to exert pressure on Taiwan, the PRC will initially seek to implement a non-LOAC based regime in order to avoid the implication that an armed conflict has commenced. Perhaps they will initially declare a weapons-based “quarantine” as the United States did during the Cuban missile crisis. However, the PRC would need to be very careful in how this interdiction regime was described, and where it was implemented. This is not least because should that interdiction regime look and operate like a LoNW blockade, this could, as a matter of law, actually signal the commencement of the armed conflict. Additionally, it could also invoke an obligation to thenceforth apply IAC LOAC, which in turn brings with it implications for third States – such as a potential need to make a decision about neutrality – which the PRC may wish to avoid triggering.

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Rob McLaughlin is a Professor of Military and Security Law at UNSW Canberra and a Professor of International Law at Australian National Centre for Ocean Research and Security.