Sovereignty Amidst Sea-Borne Conflict: The Evolving Jurisprudence of Neutrality in Naval Warfare

The concept of neutrality in naval warfare represents one of the most complex balancing acts in the corpus of international law. It seeks to reconcile the sovereign rights of states to remain outside of a conflict with the military imperatives of belligerents who wish to deny their enemies any strategic advantage. While the roots of this legal framework are found in the 1907 Hague Conventions, the evolution of maritime technology, the adoption of the United Nations Convention on the Law of the Sea (UNCLOS), and the shift toward collective security under the UN Charter have fundamentally altered the landscape. Today, the law of neutrality is not merely a static set of prohibitions but a dynamic and often contested field of jurisprudence where traditional rights of commerce collide with modern naval exclusion zones and cyber-maritime operations.

To understand the current state of these rights and duties, one must first engage with the normative friction between the Nineteenth-century ideals of absolute neutrality and the contemporary reality of qualified neutrality. The traditional view, codified in the Hague Convention XIII Concerning the Rights and Duties of Neutral Powers in Naval War, emphasized a rigid impartiality. However, the rise of the UN Security Council as the arbiter of international peace has introduced a layer of complexity: can a state remain strictly neutral when the Security Council has identified an aggressor? This inquiry forms the backdrop for any modern analysis of neutral rights at sea.

What are the duties of a neutral state in naval warfare?

The duties of a neutral state are traditionally categorized into three pillars: abstention, impartiality, and prevention. Under the Hague Convention XIII, these duties are designed to ensure that neutral territory—and specifically neutral waters—do not become a base of operations for belligerent forces. The duty of abstention requires that the neutral government itself refrain from providing any direct military assistance to the warring parties. This includes the prohibition on supplying warships, ammunition, or any material of war. While a neutral state is not generally required to prevent its private citizens from exporting arms (as noted in Article 7 of Hague XIII), the state itself must remain disconnected from the belligerents' war machines.

The duty of impartiality is perhaps the most scrutinized. It dictates that any regulations or restrictions imposed by the neutral state—such as those regarding the entry of warships into its ports—must be applied equally to all belligerents. If a neutral state allows a ship from Belligerent A to refuel, it must offer the same privilege to Belligerent B under the same conditions. This impartiality is the bedrock of the neutral status, signaling to the international community that the state does not favor the political or military outcomes of the conflict.

Finally, the duty of prevention, or more accurately, the duty of surveillance and enforcement, requires the neutral state to use the means at its disposal to prevent violations of its neutrality within its jurisdiction. This includes preventing the fitting out or arming of any vessel intended to cruise or engage in hostile operations against a power with which the neutral is at peace. A critical component of this duty is the obligation to intern belligerent troops or warships that remain in neutral territory beyond the permitted time limits. Traditionally, a warship is permitted to stay in a neutral port for no more than 24 hours, except in cases of stress of weather or damage requiring repair. The S.S. Wimbledon case (PCIJ, 1923), while primarily about canal transit, underscored the principle that a state's sovereign decision to remain neutral carries with it a rigorous obligation to control its territory against belligerent misuse.

The Scope of Neutral Jurisdiction and the Inviolability of Territory

The legal sanctity of neutral waters is articulated in Article 1 of Hague XIII, which forbids any act of hostility by belligerent warships in the territorial sea of a neutral power. This includes capturing vessels or exercising the right of visit and search. The jurisprudence of the International Court of Justice (ICJ) has consistently upheld the principle of territorial integrity. In the Corfu Channel case (1949), while the focus was on the right of innocent passage, the Court emphasized that every state has an obligation not to allow knowingly its territory to be used for acts contrary to the rights of other states. In the context of naval warfare, this means a neutral power cannot permit its waters to become a sanctuary from which a belligerent can launch attacks or retreat to safety with impunity.

Can a neutral state trade with belligerents during war?

The intersection of neutral commerce and belligerent rights is the most volatile area of naval warfare law. Historically, the right of neutral states to continue trading with all parties was a point of pride, yet it was always tempered by the belligerent’s right to prevent the enemy from receiving supplies that could sustain its war effort. This tension is managed through the doctrines of contraband, blockade, and the right of visit and search. Under customary international law and the San Remo Manual on International Law Applicable to Armed Conflicts at Sea (1994), a neutral state may indeed continue to trade with belligerents, but this trade is subject to significant risks and legal hurdles.

Contraband refers to goods which are ultimately destined for a belligerent and are susceptible for use in war. Belligerents have the right to intercept neutral merchant vessels on the high seas to search for contraband. If found, the goods—and sometimes the vessel itself—may be subject to capture and condemnation by a prize court. The distinction between absolute contraband (military equipment) and conditional contraband (food or fuel that could be used by the military) has become increasingly blurred in total war scenarios, leading to significant disputes between neutral powers and powerful navies. The 1909 Declaration of London attempted to categorize these items, but it was never fully ratified, leaving much of the practice to customary law and the updated guidance in the San Remo Manual.

Modern Maritime Exclusion Zones and Neutral Rights

A significant modern challenge to neutral trade is the declaration of maritime exclusion zones (MEZs) or war zones. During the Falklands/Malvinas Conflict and the Iran-Iraq War (the Tanker War), belligerents declared vast areas of the ocean off-limits to neutral shipping. The legal status of these zones is highly controversial. While the San Remo Manual acknowledges that a belligerent may establish such zones as a matter of military necessity, it stresses that the declaration of a zone does not absolve the belligerent of its duties under international humanitarian law. A neutral state retains the right to freedom of navigation on the high seas, and any interference with neutral shipping within an exclusion zone must be proportionate and necessary. The ICJ’s Oil Platforms case (2003) further explored the limits of military action against neutral commercial interests, emphasizing that attacks on neutral vessels (in that case, tankers) must meet a high threshold of military justification to be considered lawful self-defense.

The right of a neutral to engage in commerce is not an absolute right to be free from interference, but rather a right to be free from arbitrary or unlawful interference that exceeds the established rules of contraband and blockade.

How does UNCLOS affect neutrality at sea?

The relationship between the 1982 United Nations Convention on the Law of the Sea (UNCLOS) and the law of naval warfare is a subject of ongoing academic and judicial debate. UNCLOS is primarily a peace-time treaty, but its provisions regarding maritime zones—territorial seas, contiguous zones, Exclusive Economic Zones (EEZ), and the high seas—directly impact the geographic scope of neutral rights. Article 88 of UNCLOS states that the high seas shall be reserved for peaceful purposes, a clause that some scholars argue creates a normative tension with the conduct of naval hostilities.

The primary impact of UNCLOS on neutrality lies in the expansion of coastal state jurisdiction. When a neutral state claims a 200-nautical-mile EEZ, the question arises: do belligerents have the same rights to conduct hostilities in that EEZ as they do on the high seas? The prevailing view, supported by the San Remo Manual, is that while the EEZ remains neutral territory for the purpose of the coastal state’s economic rights, it does not possess the same level of inviolability as the 12-nautical-mile territorial sea. However, belligerents must have due regard for the rights and duties of the neutral coastal state, particularly concerning artificial islands, installations, and the protection of the marine environment. This due regard obligation, found in UNCLOS Article 58(3), serves as a bridge between the law of the sea and the law of armed conflict.

Transit Passage and Innocent Passage

Another critical area of intersection is the regime of transit passage through international straits and innocent passage through territorial seas. Under UNCLOS, all ships, including warships, enjoy the right of innocent passage through the territorial sea of a coastal state. During an armed conflict, a neutral coastal state might wish to suspend this passage for belligerent warships to preserve its neutrality. However, Hague XIII and UNCLOS provide conflicting pressures. Most practitioners agree that a neutral state may impose restrictions on the passage of belligerent warships, provided those restrictions are impartial. Yet, the right of transit passage through international straits (such as the Strait of Hormuz or the Strait of Gibraltar) is more robust and generally cannot be suspended even during conflict, creating a potential loophole where belligerent forces can transit through neutral waters legally despite the general rule of inviolability.

The Paradigm Shift: The UN Charter and Non-Belligerency

The most profound change to the rights and duties of neutral states since the early 20th century is the advent of the United Nations Charter. Under Article 2(4), the use of force is generally prohibited, and under Chapter VII, the Security Council has the power to identify an aggressor and mandate that member states take action. This has led to the concept of qualified neutrality or non-belligerency. If the Security Council mandates sanctions or military action against a specific state, other member states cannot claim traditional neutrality as a justification for failing to comply with the Council's decisions. Article 103 of the Charter explicitly states that obligations under the Charter prevail over any other international agreement, including the Hague Conventions.

This creates a hierarchy of legal obligations. A state may choose not to participate in hostilities (remaining a non-belligerent), but it may be legally required to deny certain rights to the aggressor state—such as port access or trade—that it would otherwise be required to provide under the principle of impartiality. The 1994 San Remo Manual reflects this by noting that the rights and duties of neutral states are subject to any relevant decisions of the UN Security Council. This transition from a bilateral view of conflict (Belligerent vs. Belligerent) to a collective security view (Community vs. Law-breaker) has fundamentally narrowed the scope for absolute neutrality in the modern era.

Cyber Warfare and Neutral Obligations

As naval warfare enters the digital age, the duties of neutral states are being tested by cyber operations. If a belligerent uses a neutral state's undersea fiber-optic cables or satellite ground stations to launch a cyber-attack against an enemy’s naval command and control systems, has the neutral state violated its duty of prevention? The Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations suggests that the law of neutrality applies to the cyber domain. A neutral state must not allow its territory (including its cyber infrastructure) to be used by belligerents for hostile acts. However, the technical challenge of attributing cyber-attacks and the ubiquitous nature of dual-use infrastructure make this duty extraordinarily difficult to fulfill. This remains one of the most significant legal ambiguities in contemporary maritime law.

Conclusion

The rights and duties of neutral states in naval warfare remain a vital, albeit strained, component of the international legal order. While the 1907 Hague Convention XIII provides the foundational architecture, its application is now filtered through the prisms of UNCLOS, the UN Charter, and the practical guidance of the San Remo Manual. The core principle—that a neutral state must remain apart from the conflict and that its territory must be respected—persists, but it is no longer absolute. The rise of collective security and the complexities of modern maritime commerce have transformed neutrality into a status characterized by qualified obligations and shifting jurisdictional boundaries.

As maritime conflicts continue to evolve, particularly with the introduction of autonomous systems and cyber capabilities, the international community must grapple with the need for a more precise codification of neutral rights. The current reliance on customary law and non-binding manuals, while useful, leaves neutral states in a precarious position between belligerent demands and their own sovereign interests. Future jurisprudence, whether from the ICJ or specialized maritime tribunals, will likely need to address the definition of due regard in the EEZ and the limits of neutral state liability in an era of interconnected global trade and digital warfare. Ultimately, the law of neutrality serves as a necessary buffer, preventing the horizontal escalation of conflict and preserving the stability of the global maritime commons.