Defense Journal Research Summary • UNCLOS • 1884 Convention • International Cooperation
In recent years, Taiwan's undersea cables have been frequently severed. Beyond the usual causes of natural cable damage, these incidents may also involve gray-zone tactics deployed by the PRC's "shadow fleet." Composed of flags of convenience vessels, these fleets are suspected of targeting undersea communications infrastructure with the intent to undermine Taiwan's digital resilience. International law, such as the United Nations Convention on the Law of the Sea (UNCLOS), grants authority for cable sabotage on the high seas to the vessel's flag state, leaving a gap in effective third-party sanctions or enforcement mechanisms. Taiwan is urged to establish an interagency response platform, actively participate in international submarine cable protection mechanisms, and curb the expansion of the shadow fleet. Protecting undersea cables is not merely a technical challenge -- it is a strategic imperative for preserving peace and global connectivity.
The term "shadow fleet" originally referred to Russia's aging tanker fleet assembled to circumvent international sanctions, using frequent flag changes, AIS shutdowns, and shell companies to transport oil. The PRC has now adapted the same playbook for gray-zone operations against submarine cables: flags of convenience (FoC) vessels carry out cable sabotage, exploiting their civilian identity to avoid military confrontation while using flag-state jurisdiction as a legal shield against prosecution by victim states.
In January 2025, the Tanzanian-flagged cargo vessel "Xing Shun 39" (owned by a Hong Kong company) dragged anchor with AIS off, severing the Taiwan-Asia-US Cable in waters north of Taiwan. In February 2025, the Togo-flagged "Hong Tai 58" cut the Taiwan-Penghu submarine cable. Earlier, in November 2024, the Chinese-registered "Yi Peng 3" was implicated in cutting submarine cables in the Baltic Sea, underscoring that these are not isolated accidents but part of a systematic gray-zone pattern.
| Characteristic | Rating (Taiwan Cases) | Explanation |
|---|---|---|
| Ambiguity | 5/5 | FoC vessel cover makes accident vs. deliberate act indistinguishable |
| Deniability | 3/5 | Shell companies and layered flag states obscure the controlling party |
| Gradualism | 2/5 | Each cable break appears isolated; cumulative impact only emerges over time |
Taiwan currently has 14 international and 10 domestic submarine cables. Matsu has only 2 external cables, and Kinmen only 1 plus 1 backup. Cable breaks have risen sharply: the annual average of 7-9 jumped to 12 in 2023, and 4 occurred in just the first 2 months of 2025. This trend closely correlates with expanded shadow fleet activity.
The combination of these provisions creates an "enforcement vacuum": even when a victim state has ample evidence of deliberate cable sabotage, it must rely on the flag state to initiate criminal proceedings. Shadow fleets deliberately register under states with weak enforcement capacity or no motivation (e.g., Tanzania, Togo, Cameroon), precisely exploiting this gap.
However, the 1884 Convention currently has only 36 signatories, and neither Taiwan nor the PRC is a party. Thus, despite its theoretically stronger legal tools, the convention faces fundamental legal barriers in actual application to Taiwan Strait cable incidents.
This amendment strengthens Taiwan's enforcement within its territorial waters and EEZ, but jurisdiction over foreign FoC vessels operating on the high seas or in other states' waters remains strictly constrained by the international legal framework. Possible future legal paths include "supplementary jurisdiction" (using cable landing on Taiwanese territory as the jurisdictional nexus) and "universal jurisdiction" (treating cable sabotage as an international crime against global communications security).
Establish a standing interagency coordination platform comprising the Ocean Affairs Council, Ministry of Transportation, Ministry of National Defense, and National Security Council. Develop an automated cable-alert system that detects anomalous vessel behavior near cable routes in real time and triggers response protocols.
Build a shadow fleet database and share it with the International Cable Protection Committee (ICPC), maritime insurers, and port states. Since September 2024, 96 suspect vessels have been tracked; this list should be institutionalized, jointly maintained with allies, and updated in real time.
Actively engage with the 2024 New York Joint Statement on Security and Resilience of Undersea Cables (17 signatory nations), the QUAD Cable Connectivity Partnership, and the G7 Shadow Fleet Task Force. Through allied diplomatic support, expand Taiwan's international visibility and participation in cable-protection mechanisms.
Draft domestic legislation authorizing the Coast Guard to intercept foreign vessels suspected of cable sabotage within territorial and contiguous waters. Advance the legal argument for "supplementary jurisdiction" using cable landings on Taiwanese territory as the jurisdictional nexus. The long-term goal: push for submarine cable sabotage to be recognized under "universal jurisdiction."
Apply diplomatic pressure on FoC flag states to fulfill their "genuine link" obligations under UNCLOS Article 94 and vessel registration responsibilities under IMO Resolution A.1192(33). Economic measures such as port state control (PSC) inspections and insurance restrictions can be leveraged against non-compliant flag states.
Upgrade Maritime Domain Awareness (MDA) capabilities by integrating AIS, SAR satellite imagery, and AI algorithms (as demonstrated by this monitoring site) for 24/7 vessel tracking and anomaly detection. Advance implementation of the US-Taiwan Coast Guard MOU to strengthen joint patrols and intelligence sharing.
Through allies that are UNCLOS members (such as Palau), bring cases before the International Tribunal for the Law of the Sea to establish international precedent for cable protection. Simultaneously pursue civil litigation against shadow fleet owners to impose economic accountability and raise the cost of gray-zone operations.
UNCLOS Article 113 requires states parties to enact domestic laws penalizing deliberate or negligent damage to submarine cables on the high seas. However, Articles 92 and 94 stipulate that vessels on the high seas are subject exclusively to flag-state jurisdiction -- third-party states have no enforcement authority. This means that even with clear evidence of cable sabotage by a foreign vessel, the victim state cannot detain or penalize the ship and must rely on the flag state's cooperation, which is often lacking in motivation or capacity, creating a critical enforcement gap.
The 1884 Convention's Article 2(1) criminalizes deliberate cable damage, and Article 8(2) provides a legal basis for victim states to exercise "supplementary jurisdiction" when the flag state fails to act -- a more powerful enforcement tool than UNCLOS offers. However, with only 36 signatories and neither Taiwan nor the PRC being parties, the convention does not legally apply to Taiwan Strait cable incidents.
The PRC uses civilian vessels registered under third-country flags (flags of convenience) to sabotage submarine cables, hiding behind UNCLOS's flag-state exclusive jurisdiction to block victim-state enforcement. This tactic weaponizes "civilian identity" as a legal shield -- avoiding military escalation while sustaining infrastructure damage. It is the core strategy of gray-zone lawfare.
Key methods include: frequent name and flag changes to erase identity continuity; AIS shutdowns to disappear from monitoring systems; shell companies to obscure beneficial ownership; and ship-to-ship (STS) transfers to avoid port inspections. The "Xing Shun 39" exemplifies this: Tanzanian flag, Hong Kong company, AIS off at time of incident -- the full evasion playbook.
The 2023 amendment to the Telecommunications Management Act Article 72 criminalizes damage to cable landing stations and connected cables, providing a domestic legal foundation. However, jurisdiction is mainly limited to Taiwan's territorial waters and EEZ; enforcement over foreign vessels in international waters remains constrained by international law. Criminal damage statutes may also apply but face similar extraterritorial jurisdiction challenges.
The 2024 New York Joint Statement on Security and Resilience of Undersea Cables (17 signatory nations); the QUAD Cable Connectivity Partnership; the G7 Shadow Fleet Task Force; IMO Resolution A.1192(33) requiring enhanced vessel registration and flag-state responsibility; and the Tokyo MOU providing a regional port state control inspection framework. Taiwan can participate indirectly through allies to strengthen cable protection capabilities.