By Jao Juei-cheng 饒瑞正
The US Senate Committee on Foreign Relations has formally elevated damage to undersea cables to a national security issue, pointing to Russia and China as allegedly using tactics with low attribution risks — such as dragging anchors — to threaten subsea infrastructure. Meanwhile, the rupture of the Taima No. 3 (台馬三號) cable connecting Beigan (北竿) and Dongyin (東引), part of the Matsu islands of Lienchiang County that sit close to the Chinese coast, highlights the continued structural vulnerabilities in Taiwan’s offshore communications resilience. The situation in the Strait of Hormuz further demonstrates how global energy shipping lanes can be strategic chokepoints for digital data flows. Together, the three developments point toward a common conclusion: Undersea cables have become a front line of maritime security in the digital age. In response to the risks, Taiwan should consider designating “sensitive maritime zones” around critical undersea cable routes, landing stations and offshore communication corridors. The zones must not be treated as no-sail areas, but neither can they become tools for the arbitrarily expansion of maritime jurisdiction.
Under international maritime law, territorial seas and exclusive economic zones (EEZs) have substantive legal distinctions that must be reflected in governance measures and implementation. Within territorial waters, a state enjoys sovereignty, so establishing sensitive maritime zones to protect undersea cables, ports, military facilities and other critical infrastructure — along with implementing navigation controls, anchoring bans, fishing trawl restrictions, reporting requirements and, when necessary, temporary navigation prohibitions — has a relatively solid legal basis. Even so, the right of innocent passage must still be respected. Any restrictions should have clear legal foundations and comply with the principles of necessity, proportionality and nondiscrimination. Within EEZs, the situation becomes more delicate. An EEZ is not sovereign territory, meaning foreign vessels can enjoy freedoms of navigation, undersea cable laying and other internationally lawful uses of the sea. Coastal states cannot intercept, expel or permanently bar foreign vessels simply because they approach submarine cables. As such, when designating sensitive zones within the EEZ, the more legally sustainable approach is to frame them as “risk governance” rather than exclusionary zones. In practice, the sensitive areas could function as priority monitoring zones, navigation warning areas, no-anchoring and no-trawling zones, restricted seabed engineering and sand extraction areas, and regions for identifying abnormal vessel behavior. Authorities could integrate automatic identification system vessel tracking data, radar, satellite imagery, seabed mapping and cable anomaly signals to identify high-risk activities such as repeated crossings, slow dragging movements, abnormal loitering or vessels disabling their identification systems. At the same time, governments should establish mechanisms for real-time industry reporting, interagency coordination, evidence retention, port inspections and rapid repair responses. Establishing maritime zones would be to exercise due diligence under international maritime law. States are not expected to guarantee that undersea cables will never be damaged, but when risks are foreseeable, they are obligated to take reasonable preventive measures within the limits of their lawful authority. The value of governing sensitive maritime zones lies not in blanket exclusions, but in balancing cable security, navigational freedom and maritime order through reasonable, proportional, nondiscriminatory and risk-based governance. If Taiwan can institutionalize such a governance model, it could transform the Matsu experience into an important international example of maritime security management. Jao Juei-cheng is a professor in National Taiwan Ocean University’s Institute of the Law of the Sea and is honorary chairman of the Taiwan Maritime Law Association. Translated by Gilda Knox Streader