International Law Neutrality
Elizabeth Chadwick
  • LAST REVIEWED: 12 May 2017
  • LAST MODIFIED: 27 March 2014
  • DOI: 10.1093/obo/9780199796953-0060


On the outbreak of war, states which do not wish to participate declare neutrality. Also termed “armed neutrality,” a stance of neutrality during war is distinguished from “neutralization” (a permanent status of neutrality), or the neutrality maintained by humanitarian NGOs and UN peacekeeping units. Neutrality during war has for centuries performed a crucial function within the laws of international armed conflict, as the status helps to curtail the spread of hostilities by promoting neutral abstention and an attitude of impartiality toward the belligerents. Therefore, neutral states remain at peace with other neutral states and at peace with the belligerents to the greatest extent possible. In return, the belligerents are obligated to respect neutral territory and jurisdiction (land, sea, air, etc.) and innocent neutral trade. Such seeming simplicity as regards the mutuality of neutral and belligerent rights and duties is not the entire picture, however, as rules of neutrality between states do not necessarily bind private individuals. In other words, so long as neutral governments officially abstain from assisting either party to the hostilities, and remain impartial, they may feel more—or less—inclined to prohibit their citizens from engaging in such activities as foreign enlistment. Further, neutrals may still benefit from foreign wars indirectly. Variations between neutrals as to the precise scope of their obligations can arise from neutral state administrative complexity and/or coercive weakness, such that a variety of commercial opportunities may in fact remain for neutral citizens to exploit, e.g., to equip, supply, and/or finance foreign wars. On the other hand, the UN Charter of 1945 appears at first sight to have altered this centuries-old accommodation between war and neutrality. Charter Article 2(4) prohibits aggression, and is reinforced in Charter Chapter VII by Security Council enforcement powers which are legally binding on states. However, the Security Council rarely utilizes these powers, which leaves equal sovereign states relatively free to determine for themselves—initially, at least—the lawfulness of force utilized in international relations, as in self-defense, pursuant to Charter Chapter 51, and/or during liberation wars in which a “people” fights for their self-determination. Accordingly, the preponderance of the available evidence indicates a high degree of ongoing support for neutrality within international society.

General Overviews

The slow evolution of neutral principles up until the League of Nations era can be found in the four volumes of Neutrality: Its History, Economics and Law (Jessup, et al. 1935–1936). In essence, the core principles of neutrality are few and are designed to ensure that neutral states abstain from the hostilities and adopt a nondiscriminatory attitude of impartiality toward the belligerents. The main rights and duties of neutral and belligerent states include the following: neutral territory (land, sea, air, etc.) is inviolable; neutrals may utilize force to repel belligerent violations of their rights; in most circumstances, defensive neutral force cannot be viewed as a hostile act; neutrals may afford humanitarian aid to the victims of a conflict without endangering their neutrality; belligerent forces found in neutral territory must be interned by the neutral for the duration of the hostilities; the belligerents are prohibited from recruiting military personnel in neutral territory, while neutrals should municipally prohibit their citizens from enlistment and/or from engaging in other activities of behalf of the belligerents; and the belligerents may monitor neutral trade to prevent receipt by the enemy of prohibited contraband. The inviolability of neutral territory may however depend on the context of the hostilities. International instruments such as the 1907 Hague Convention V, relating to the rights and duties of neutral powers in case of war on land, and the 1907 Hague Convention XIII, applicable to neutral powers in naval warfare (for both see International Treaties), differ in detail as to this point. For this reason, general overviews on neutrality tend to be divided in approach. Neff 2000 provides fairly generic discussions of both land and sea neutrality, while the San Remo Manual 1994 (Doswald-Beck 1995), Heintschel von Heinegg 2006, and the Committee on Maritime Neutrality 2004 deal with maritime neutrality alone. In turn, the prohibition of aggression in UN Charter Article 2(4) and Chapter VII enforcement powers have led most modern writers to advocate a high level of tolerance for neutral flexibilities. Nonetheless, as states continue to characterize their uses of force as lawful pursuant to Charter law, and as belligerent environments continue to evolve, the currency of the core neutral principles is maintained—a point reflected by ongoing reference to neutrality in most state military manuals, in academic commentary, and in state practice. Complete, if occasionally succinct, accounts of the modern rules of neutrality are also found in Cummings 1978, Walker 2001, and the Tallinn Manual (Schmidt 2013).

  • Committee on Maritime Neutrality. “Final Report: Helsinki Principles on Maritime Neutrality: Report of the 68th Taipei, Taiwan Conference, 24–30 May 1998.” In The Laws of Armed Conflicts: A Collection of Conventions, Resolutions, and Other Documents. 4th rev. ed. Edited by Dietrich Schindler and Jiri Toman, 1425–1430. Boston: Martinus Nijhoff, 2004.

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    The Committee on Maritime Neutrality of the International Law Association produced this commentary concerning seven succinct Principles of neutral rights and duties; defines “belligerent” and “neutral” states in terms of parties and non-parties to an international armed conflict; makes clear that the Principles cannot justify or facilitate evasion of binding UN Security Council obligations.

  • Cummings, Edward R. (Capt.). “Additional Report: The Evolution of the Notion of Neutrality in Modern Armed Conflicts.” Military Law & Law of War Review 17 (1978): 37–190.

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    An unofficial and highly selective survey of US military and neutrality laws for use during modern armed conflicts; provides substantive coverage of the history and modern content of neutral rules; considers the impact of UN Security Council enforcement obligations.

  • Doswald-Beck, Louise, ed. San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 12 June 1994. Cambridge, UK: Cambridge University Press, 1995.

    DOI: 10.1017/CBO9780511622052Save Citation »Export Citation » Share Citation »

    The first comprehensive international instrument since 1913 on laws of armed conflict at sea; considers rules of neutrality throughout; paras 7–9 concern authorized Security Council enforcement actions; paras 14–22 and 23–33 consider the rules for straits, archipelagic waters, and territorial seas; paras 79–92 address means of warfare.

  • Heintschel von Heinegg, Wolff. “The Current State of the Law of Naval Warfare: A Fresh Look at the San Remo Manual.” Naval War College International Law Studies 82 (2006): 269–296.

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    Disagrees with criticism that The San Remo Manual (Doswald-Beck 1995) adopts too traditional an approach to neutrality for purposes of the UN era; argues at p. 283 that the better view is to apply essential rules of neutrality whenever the Security Council is unable to authorize enforcement action. Available online.

  • Jessup, Philip C., et al. Neutrality: Its History, Economics and Law. 4 vols. New York: Columbia University Press, 1935–1936.

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    Volume 1: Philip C. Jessup and Francis Deak, The Origins (1935), is essentially historic and strategic in outlook; Volume 2: Alison W. Phillips, and Arthur H. Reede, The Napoleonic Period (1936), and Volume 3: Edgar Turlington, The World War Period (1936), concern economic aspects; and Volume 4: Philip C. Jessup, Today and Tomorrow (1936), focuses on political and legal contexts of neutrality; coverage overall extends from the 16th century to the League of Nations era, as exemplified in treaties, state practice, and prize court decisions.

  • Neff, Stephen C. The Rights and Duties of Neutrals: A General History. Manchester, UK: Manchester University Press, 2000.

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    Provides a comprehensive survey of the history and development of laws of neutrality, from their roots in the Middle Ages through to the end of the 20th century; includes relevant doctrinal debates; cited extensively by contemporary scholars.

  • Schmidt, Michael N., ed. Tallinn Manual on the International Law Applicable to Cyber Warfare. Cambridge, UK: Cambridge University Press, 2013.

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    Assumes the operability of laws of neutrality in cyber military operations; the last chapter, pp. 248–256, outlines neutral and belligerent rights and duties as regards neutral cyber infrastructures located within neutral territory, those under exclusive neutral control, or those which have neutral nationality and are located outside belligerent territory.

  • Walker, George K. “Neutrality and Information Warfare.” Naval War College International Law Studies 76 (2001): 233–263.

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    Discusses neutrality in terms of its elusiveness in the sense of a positivist, black-letter approach; argues strongly for the promotion of neutrality due to its restraining effects on the conduct of war, particularly in the Charter era; considers neutrality to be sufficiently flexible and adaptable to apply to “information warfare.” Available online.

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