Introduction

In recent decades, there have been increasing concerns in Japan over the growing threat of grey zone challenges. The East China Sea has been a key arena in which such grey zone challenges manifest. Here, Japan has expressed concerns over Chinese maritime activities that seek to unilaterally change the status quo, especially in the waters surrounding the disputed Senkaku/Diaoyu Islands. Japan’s response to grey zone challenges may face potential limitations arising from domestic legislation; however,  it is seeking to strengthen relevant capabilities through increased funding and inter-agency cooperation.

Characterizing Grey Zone Challenges

Within the security community, the ‘grey zone’ concept has been used in both academic and policy circles to describe certain threats in the geopolitical environment of today (Marsh, 2024; The International Institute of Strategic Studies, 2023; US Department of Defense, 2022). Though there is much debate over the characterization and definition of the grey zone, there seems to be a general recognition that the grey zone entails tactics and activities that remain below the threshold of attack or war, yet may appear to lie within the space between war and peace (US Special Operations Command, 2015). In the Japanese context, one of the earliest uses of ‘grey zone’ terminology can be found in the 2010 National Defense Program Guidelines (National Institute of Defense Studies, 2023), where grey zone challenges are defined as “confrontations over territory, sovereignty and economic interests,” which, crucially, “are not to escalate into wars” (Ministry of Defense of Japan, 2010). More recently, the Defense of Japan 2024 White Paper builds on the definition of the grey zone, notably extending the scope of interests to include those in the maritime domain and adding an element of “forceful organization” to, for instance, “alter the status quo” (Ministry of Defense of Japan, 2024).

The Grey Zone Challenge Faced by Japan

Japan’s concerns surrounding grey zone challenges primarily lie in the maritime domain of the East China Sea, where there have been longstanding territorial tensions with China over the disputed Senkaku Islands (referred to by China as the Diaoyu Islands). Specifically, Japanese policy documents have outlined concerns over how China appears to be attempting to forcefully modify the status quo through activities such as continuous intrusions by China Coast Guard (CCG) vessels into Japanese territorial waters—especially those surrounding the Senkaku/Diaoyu Islands (Ministry of Defense of Japan, 2024). Amidst such intrusions, it is argued that CCG ships engage in coercion by approaching Japanese fishing vessels within Japanese territorial waters (Ministry of Foreign Affairs of Japan, 2024). A  key aspect of such ‘grey zone’ tactics lies in the employment of legal tools, with a particular emphasis on domestic legislation such as the 2021 CCG Law (Sato, 2023). There have been concerns raised over various articles in the Law, for instance, regarding Article 3, which empowers the CCG in “waters under the jurisdiction of China” (Coast Guard Law of the People's Republic of China, 2021). When situated within the context of China’s jurisdiction claims over disputed maritime areas such as the Senkaku/Diaoyu Islands, the potential application of the CCG Law would naturally be worrying to its neighbors, with concerns having been expressed by various countries including Japan, Indonesia, and the Philippines (Asia Maritime Transparency Initiative, 2021). For instance, Japan’s Ministry of Foreign Affairs has highlighted how the CCG Law may have potential inconsistencies with international law, for instance in the ambiguity of its “applicable sea area” and the provisions surrounding the “use of weapons” (Ministry of Foreign Affairs of Japan, 2024). The recent CCG Order #3, which authorizes the CCG to detain foreign vessels or individuals suspected of violating domestic Chinese laws in waters under its jurisdiction, also runs into similar issues of ambiguity surrounding its application (Hui & Yeung, 2024).

The Current Japanese Response

At present, the maritime intrusions by CCG vessels are met with responses by Japanese Coast Guard (JCG) patrol vessels on the front lines along with diplomatic protests at the government level. However, there are certain limitations to such an approach. Firstly, the domestic JCG Act and Police Duties Execution Act collectively outline strict provisions on the use of force and weapons, particularly against foreign governments or naval vessels. Specifically, under domestic law, JCG personnel are only authorized to use force against warships and vessels owned or operated by a foreign government solely for non-commercial purposes. Even so, they have to operate within strict boundaries even under circumstances of self-defense (Kanehara, 2023). In the event of further escalation beyond the capabilities of the JCG, Article 82 of the Self-Defense Forces (SDF) Law allows for Maritime Security Operations (MSOs) to be undertaken at sea by SDF units when it is deemed “necessary to protect life or property or maintain public order at sea,” allowing the Japanese Maritime Self-Defence Forces (JMSDF) to take over from the JCG (Furuya, 2021). Notably though, MSOs are still considered law-enforcement operations where similar limits on the use of force are applied to the JMSDF (Furuya, 2019). Crucially, there may only be less stringent limits on the use of weapons, even for self-defense, in situations where Japan is suffering from, or faces the threat of, an “armed attack,” where a Defence Operation can be conducted under Article 76 of the SDF Law (Furuya, 2019). Therefore, the limited use of force in grey zone tactics employed by adversaries may not meet the threshold needed under domestic Japanese legislation to justify a sufficiently assertive response, posing a potential challenge to the protection of its sovereign rights and interests. This difficulty could be further compounded by comparatively weaker capabilities compared to its foreign counterparts, as the CCG is said to have outnumbered the JCG in measures of physical assets and budgeting (Pacific Forum, 2021).

The Way Forward for Japan

Japan recognizes the need to strengthen its ability to counter such grey zone challenges, with the JCG making a record-high 293.5 billion yen funding request in the fiscal 2025 budget, of which 3.43 billion yen is planned for the building of a new multipurpose patrol vessel (Kyodo News, 2024). Furthermore, enhancing JMSDF-JCG cooperation has been a key priority, with the introduction of the Control Guideline being one such measure to strengthen joint responses to grey zone challenges (Furuya, 2023). Finally, changes to legislation are unlikely in the near-term, but could be a growing possibility in light of how Japan is strengthening its defense capabilities and taking on a more assertive role in the regional security architecture.