The approach of the book will be to consider these issues in six parts.
Chapter 1 will address the principles of general international law governing the use of force in incidents below the threshold of war. This is highly topical but also quite contested. Much of the focus is on terrestrial rather than maritime incidents as well, so it will be necessary to apply the general principles to the specific context of the law of the sea. The chapterwill include discussion of the United Nations Charter and related customary international law, as well as the key cases: the Corfu Channel Case (UK v Albania), the Nicaragua v the US,2 the Saiga Case (St Vincent and the
Grenadines v Guinea), the Oil Platforms Case (Iran v the US) and the South China Sea Arbitration (Philippines v China).
Chapter 2 will consider the concepts of unit and collective self-defence and draw a distinction with the concept of national self-defence. The use of force by warships in self-defence is first a question for commanders and should not necessarily amount to a conflict between states. It can extend only to the immediate defence of the warship, task group or vessels under escort, from targets which pose a direct threat. It does not extend to targets which do not pose a direct threat. Unit self-defence also does not extend to foreign warships or civilian vessels under escort unless there is agreement between the flag states concerned. In order to guide decisions by commanders, different indicia have developed for determining when an attack at sea is actually occurring and therefore when a warship may use force in self-defence. The highly contextual nature of establishing the intent of an opposing force however illustrates the limits of law in addressing these questions.
Chapter 3 discusses proportionality in the use of force in self-defence. The approach of the cases limits this to the immediate defence of the unit under attack, essentially a unit self-defence approach. Use of force beyond that requirement can be the point which reaches the threshold for the application of the law of aimed conflict. Despite the position in some naval and military manuals that it applies at the fust shot, the cases are much more restrained. The cases actually treat most incidents as questions for the jus ad bellum rather than the jus in bello.
Chapter 4 turns to the application of use force principles in the maritime zones under the law of the sea. Territorial and internal waters are subject to sovereign national jurisdiction and are the most restrictive in terms of the ability of warships to use force in self-defence. Conversely, a warship which does not respect the sovereignty of the coastal state does not necessarily pose a lethal threat. The coastal state should distinguish between threats to sovereignty and threats to life - non-lethal threats demand no more than non-lethal responses. The Swedish response to submerged contacts in the 1980s is an example of state practice, and the South China Sea Arbitral Award provides some guidance as to the law.
Chapter 5 deals with the most sensitive issue of navigation in straits and archipelagos. Whilst the Corfu Channel Case provides invaluable guidance, it precedes the more permissive concept of transit passage in the 1982 Convention. The Oil Platforms Case is reasonably clear on the right of escort through straits. Arguably, there should also be some right for warships to clear obstructions to their passage, such as mines, as incidental to the right of passage in the normal mode. This should occur within the limits of unit self-defence, however, and not amount to deliberate violations of the sovereignty of the coastal state. Despite the common feature of passage in the normal mode, the considerations for archipelagic sea lanes are different. The much greater extent of the intrusion of such lanes into the archipelagic state, and the lack of a right to visit ports in the state and remain in archipelagic sea lanes passage, means that escort and clearance of obstructions should be more limited.
Chapter 6 concerns the regimes for the high seas, exclusive economic zone and the contiguous zone. Despite not being subject to sovereignty, there has been much contention over questions of escort in the EEZ and places in which there is a dispute as to whether they are high seas or EEZ. It seems clear enough that warships may escort vessels in the EEZ and the high seas and use proportional force to protect them from foreign warships. They should only protect foreign-flagged shipping from foreign warships with the agreement of the flag state, however. Warships should also not protect vessels which are deliberately violating the sovereign rights in the EEZ of foreign coastal states.
The law cannot provide all of the answers to questions concerning warships, freedom of navigation and the use of force. Still, from this analysis of the cases and examples of state practice, this book will argue for a set of rules which respects both the rights of coastal states to protect their sovereignty and for warships to navigate lawfully, while outlining the limits to the rights of each. As this book will conclude, there are 25 identifiable rales which can guide commanders and decision makers in government as to what is and is not acceptable - addressing issues of legitimacy as much as legality. As stated previously, while the law alone cannot prevent conflict at sea, a lack of clarity as to such law as there is may start one.
See Ken Booth, Law, Force and Diplomacy at Sea (1985, Routledge Revivals, 2014) 111
-  The ‘MJVSaiga' (No.2) Case (Saint Vincent and the Grenadines v. Guinea) International Tribunal for the Law of the Sea, Case No 2,1 July 1999 2 Oil Platforms (Islamic Republic of Iran v United States), International Court of Justice, 6 November 2003