1 The veto (Latin, ‘I forbid’, ‘I do not allow’) generally denotes the legal power of the holder of an office, or of a legal person or organ, to prevent a certain decision from being taken, or a legal act from entering into force. One distinguishes a ‘suspensive veto’, which loses its force after a certain amount of time or because it was overruled (especially by the organ which first had taken the decision), from an ‘absolute veto’ which definitively impedes the decision or act. In present international law, the practically most important manifestation of the veto is the rule, contained in Art. 27 (3) United Nations Charter, that decisions of the UN Security Council on substantive matters must be supported by the concurring votes of the permanent members of the Security Council (see paras 9–17 below; United Nations, Security Council).
2 The veto is usually traced back to the law of the Roman Republic where it appeared in different contexts. However, the term ‘veto’ was not used at the time. Instead, the so-called intercessio, or ius intercessionis (derived from the verb intercedere, which means to intervene, or to obstruct something) was the right of a high official of the Republic (magistratus) to invalidate an official act performed by another official of the same rank, thereby preventing similar acts from being performed in the future (see Mommsen at 258–92; Bleicken  at 102). The intercessio was a corollary of the principle of collegiality according to which each office was conferred on several people (at least two) in order to prevent abuse of power. The highest Republican office, the consulate, was allocated to two consuls, each of whom could obstruct the orders and measures of the other. Further, since the middle of the 3rd century BC a tribune of the plebs (tribunus plebis) was entitled to invalidate any measure or order taken by a magistratus, in order to protect the interests of the plebs (see Bleicken  at 5–9, 74–94).
3 The modern usage of the term originates in the constitutional history of Poland. From the 16th century up to the constitutional reform of 1791, every member of the Polish parliament (Sejm) had a right of liberum veto because only a resolution unanimously adopted by both houses could become a law, provided the King approved of it. A dissent of a single member of the parliament thus prevented a resolution from being adopted (see Kutrzeba at 172, 218). In France, the constitutional convention (Assemblée nationale constituante) accorded the King a right of suspensive veto against legislative acts; that right was confirmed by the Constitution of 1791 (see Title III Chapter III Sec. III Art. 2 Constitution de 1791).
4 The term ‘veto’ was also used in the context of the election of the Pope. The ius exclusivae (right of exclusion) was a right claimed by several Catholic monarchs of Europe (the Kings of France and Spain, the Holy Roman Emperor, and, later, the Emperor of Austria) to veto a candidate for the papacy. One of these monarchs would make known to a papal conclave, through a crown-cardinal, that a certain candidate for election was considered objectionable as a prospective pope. This right seems to have first been claimed in the 17th century. It was never recognized by the papacy or the Catholic Church. The alleged right was exercised for the last time in 1903 by the Austrian Emperor Franz Joseph I to exclude Cardinal Mariano Rampolla. The conclave elected Cardinal Sarto (Pius X) instead who then absolutely forbade the ius exclusivae in the Constitution Commissum Nobis (Constitutio Commissum Nobis [20 January 1904]).
5 At present, the veto is an institution of the constitutional law of many States (see Veto). In particular, Heads of State are often entitled to veto decisions taken by the legislative bodies. Usually, such a veto has only a suspensive effect. According to Art. I Sec. 7 paras 2 and 3 Constitution of the United States of America, a bill passed by both houses of Congress must be presented to the President for his or her approval. If the President objects to the bill, he or she may return it unsigned within ten days (‘presidential veto’). The bill can then become law only with approval on reconsideration by two-thirds majorities of both houses, which thereby act to ‘override the veto’. If a bill is not returned (unsigned) by the President within ten days, or is signed and returned by the President, it becomes law, unless the Congress prevented the bill’s return by adjourning, in which case the bill dies through what is known as a ‘pocket veto’.
B. The Veto in International Law in General and in the League of Nations
6 Classical international law operated on the assumption that a sovereign State is only bound by a rule of international law to which it has freely consented (Consent). In other words, a sovereign State could object against, or ‘veto’, any change of the law having an impact on its own legal position which it disliked. That correlation between the principles of sovereignty and unanimity was described by Brierly as follows:
However, in practical terms smaller States had little influence on the development of general international law.
7 When international conferences (Conferences and Congresses, International) were institutionalized at the beginning of the 20th century, and voting, a concept alien to the traditional management of international relations, arose as a decision-making mechanism, this abstract requirement of unanimity for international law-making was translated into a procedural rule: no State could be bound without its consent—expressed by a positive vote—or, at least, against its declared dissent (International Organizations or Institutions, Voting Rules and Procedures). In the words of the President of the Second Hague Peace Conference in 1907, ‘the first principle of every Conference is that of unanimity; it is not an empty form, but the basis of every political understanding…[E]ach delegation represents a different State of equal sovereignty’ (reprinted in Claude 119). When unanimity is required, every State has a right of veto.
8 After World War I, the Covenant of the League of Nations incorporated the unanimity rule in its Art. 5 (1) as the basic premise of its voting arrangements: ‘Except where otherwise expressly provided in this Covenant or by the terms of the present Treaty, decisions at any meeting of the Assembly or of the Council shall require the agreement of all the Members of the League represented at the meeting’ (emphasis added). Although the ‘development of the League…was characterized by a constant process of encroachment on the principle of unanimity’ (Jenks  34), the most important decisions continued to require unanimity. In an advisory opinion of 21 November 1925, the Permanent Court of International Justice (PCIJ) held that the rule of unanimity, as laid down in the Covenant of the League of Nations, was ‘in accordance with the unvarying tradition of all diplomatic meetings or conferences’, and that its observance was ‘naturally and even necessarily indicated’ in an intergovernmental body such as the Council of the League, save only in explicitly excepted cases (see Interpretation of Article 3, Paragraph 2, of the Treaty of Lausanne [Frontier between Turkey and Iraq] [Advisory Opinion] at 29–30). As Sir Humphrey Waldock said, ‘the rule of unanimity underlined that the League was designed as a system of organised diplomatic cooperation, and not as a system of international government’ (Waldock 9).
C. The Veto in the UN Security Council
9 In 1945, the UN Charter instituted majority voting in all UN organs, including the Security Council. This step ‘represent[ed] the completion of a revolution of decisive importance for the future development of international organizations’ (Jenks  36). It was unexpected especially in view of the unprecedented powers conferred on the new world organization in Chapter VII of its Charter. Compared to the League of Nations, the UN was indeed ‘a body very different in character’, ‘a body working under a system of majority voting’ (Brierly 69), even if in practice decision-making by consensus became frequent, especially in the General Assembly and its committees (United Nations, General Assembly).
10 However, according to Art. 27 (3) UN Charter any decision of the UN Security Council on substantive matters—as distinguished from ‘procedural matters’ in Art. 27 (2) UN Charter—requires an affirmative vote of nine members—until the number of non-permanent members of the Council was raised from six to ten in 1963, it was seven members—‘including the concurring votes of the permanent members’. This provision is the basis of the famous and often criticized veto power of the ‘P5’, namely China, France, Russia (formerly the Soviet Union), the United Kingdom, and the United States (Art. 23 (1) UN Charter). In a statement by the delegations of the ‘four sponsoring governments’ (those just mentioned, with the exception of France) on voting procedure in the Security Council of 7 June 1945, the veto power was justified in the following terms:
11 The five States who laid claim to the veto carried the freedom they had enjoyed under general international law and in the framework of the League of Nations with them into the new organization. They became part of the collective body only with an important reservation: they cannot be obliged to take action, or to refrain from it, against their will (for the origins of the veto clause, see Fassbender  at 163–70). Although a permanent member of the Security Council numerically has the same voting power as every other member, its right of veto actually enhances this power enormously. A permanent member alone can obstruct a decision, while it needs a negative vote of at least seven non-permanent members to have the same effect.
12 While it is wrong to describe the permanent members’ position in the UN as one ‘above the law’—the P5 are bound by the same rules of the UN Charter that bind any other Member State—the permanent members clearly constitute a distinct category of the UN membership as there is not only a de facto but also a de iure inability on the part of the Security Council to pass a resolution in non-procedural matters against their will. The veto power of the permanent members was sharply criticized at the Conference of San Francisco, but the five powers insisted on the compromise on voting in the Council which had been reached at the Yalta Conference (1945). What had been controversial between the major Allies at Yalta was the right of veto of a permanent member when it was a party to a dispute laid before the UN Security Council, and the question whether the veto could be used to prevent the UN Security Council even from discussing a situation or dispute brought to its attention. In contrast, the United States, the Soviet Union, and the United Kingdom had early agreed on the core of the right of veto the major powers should possess in the new world organization. Permanent membership in the UN Security Council, together with the right of veto, was understood to be a suitable means of safeguarding their prominent position in the organization and thus in the postwar international system.
13 The right of veto of the permanent members has three major consequences that were aptly described by Hans Morgenthau: First, ‘the veto eliminates any possibility of centralized measures of law enforcement being applied against any of the permanent members’ (at 313). Secondly, because of the veto, enforcement measures are also unlikely to be taken by the Security Council against any State closely aligned with one of the permanent members (see also International Organizations or Institutions, Supervision and Sanctions). And thirdly, ‘the veto eliminates for all practical purposes the qualifications by which Article 51 [UN Charter] endeavors to subordinate the right of collective self-defence to the centralized enforcement system of Chapter VII’ (Morgenthau at 314). In other words, whenever a permanent member or one of its close allies is directly or indirectly involved in a conflict, the Council will not be able to actualize its ‘authority and responsibility’ under Art. 51 UN Charter either to stop or curtail, or to support measures taken on the ground of self-defence. But the scope of the veto power extends beyond the maintenance of international peace and security entrusted to the Security Council by Art. 24 UN Charter. In particular, the admission of new members and the suspension of membership rights (Arts 4 and 5 UN Charter) are subject to the veto just as the appointment of the Secretary-General is (Art. 97 UN Charter; United Nations, Secretary-General). Further, an amendment to the UN Charter only comes into force after it is ratified by all the permanent members of the Security Council (Arts 108 and 109 (2) UN Charter) which means that the UN Charter cannot be amended against the will of any of the P5.
14 In the practice of the Security Council, the rule embodied in Art. 27 (3) UN Charter was modified in two important ways. First, and contrary to the wording of the provision, a voluntary abstention or an absence of a permanent member came to be understood as not frustrating a non-procedural decision. Secondly, not much attention was paid to the rule according to which in decisions made under Chapter VI, and under Art. 52 (3) UN Charter, a party to a dispute shall abstain from voting (obligatory abstention) (for details, see Fassbender  178–83, 190–91). As Bailey noted, ‘the idea that a state should not be a judge in its own cause has been largely forgotten’ (at 564)—a somewhat ironic development given the fact that the intense disagreement between the United States and the Soviet Union on exactly that issue had almost thwarted the entire UN project.
15 In the first years of the UN, the issue of the so-called ‘double veto’ attracted a lot of political and academic interest. The expression was used to describe a succession of two negative votes by a permanent member: first, a negative vote is cast when a decision is taken about the preliminary question of whether a certain matter is a procedural one, with the result that the matter is declared to be non-procedural; and second, another negative vote is cast in the ballot about the non-procedural decision itself (see Liang at 134). The ‘double veto’ was based on the Four Powers’ statement on voting of 7 June 1945, referred to above (see para. 10), at the end of which it was said that in light of the rules of the UN Charter
This meant that, notwithstanding the distinction between procedural and substantive questions in the UN Charter, as a last resort a permanent member can make any matter a substantive one and then veto the proposed decision. Contrary to the concerns of the early years, the procedure of the ‘double veto’ was rarely used.
16 The veto has considerably hindered the activity of the Security Council. During the Cold War (1947–91), its use reflected the antagonism between the two blocs. Many Western motions were defeated by a Soviet veto, and vice versa. By far, most of the formal vetoes were cast by the Soviet Union, but statistics on use of the veto (see, eg, Patil 1992 and 2001; Schindlmayr 2001; Tavernier  at 950–51) are problematic because they do not take account of the many cases in which a threat of using the veto was enough to frustrate an initiative and resulted in a draft resolution not being put to a vote. As a diplomat experienced in the work of the Security Council remarked, the threat to use the veto ‘normally suffices to bring the P5 to their exclusive internal negotiation table … until, sometimes after months and months, they have agreed a proposal to submit to the non-permanent members who normally follow suit’ (Eitel 1443–44). Such unanimity of the P5 could, for instance, so far not be achieved with regard to an admission of the Republic of China (Taiwan), or of the Republic of Kosovo, or of the State of Palestine to the United Nations (UN).
17 The criticism that the veto not only paralyzes the Security Council but also is incompatible with the principle of sovereign equality of all UN Member States, already voiced at the founding conference of San Francisco, never fell silent (States, Sovereign Equality). The Uniting for Peace Resolution (1950) was a prominent attempt to confer the competence for measures maintaining or restoring international peace and security from a Security Council blocked by the veto to the General Assembly which can take majority decisions. After the end of the Cold War, many reform proposals addressed the issue of membership in the Council and the right of veto of the permanent members (see Fassbender 1998, 2003, and 2004). A great number of States, among them those united in the Non-Aligned Movement (NAM) and the African Union (AU), have demanded an abolition or considerable restriction of the right of veto. Other efforts have aimed at an agreement on ‘informal restrictions’ on the use of the veto. In 1993, the General Assembly established an Open-ended Working Group ‘to consider all aspects of the question of an increase in the membership of the Security Council and other matters related to the Council’ (UNGA Res 48/26 at para. 1). Among these ‘other matters’, the veto is one of particular importance. The working group, later renamed ‘Open-ended Working Group on the Question of Equitable Representation on and Increase in the Membership of the Security Council and Other Matters related to the Security Council’, is still in existence but has failed so far to produce an agreement which could procure a majority required for Charter amendments (see Arts 108 and 109 UN Charter). The same is true for another UN forum for advancing Security Council reform, the so-called ‘Intergovernmental Negotiations’, initiated by the General Assembly in 2008 (UNGA Decision 62/557 GAOR 62nd Session Supp 49 vol 3, 106).
D. The Veto in Other International Organizations
1. The Rule of Unanimity
18 In a number of international organizations, decision-making is still governed by the rule of unanimity, reflecting the principle of sovereign equality of States in the strictest sense. In other organizations, constitutional provisions require that certain decisions are to be taken unanimously. In both cases one may speak of a veto power in a wider sense because every Member State is able to prevent a decision from being taken.
19 An example of an organization which follows the unanimity rule is the Organization of the Petroleum Exporting Countries (OPEC). Art. 11 C OPEC Statute provides that all decisions of the Conference (which consists of delegations representing the member countries) other than on procedural matters ‘shall require the unanimous agreement of all Full Members’. Another example is provided by the Moselle Commission established by the 1956 Moselle Convention concluded between Germany, France and Luxembourg (Moselle River; see Art. 44 Moselle Convention).
20 On the other hand, Art. 10 North Atlantic Treaty of 1949 is an example of a constitutional rule requiring unanimity for a particular decision. According to this Article, the parties to the treaty ‘may, by unanimous agreement, invite any other European State in a position to further the principles of this Treaty and to contribute to the security of the North Atlantic area to accede to this Treaty’. Similarly, Art. 20 (a) (vi) Statute of the Council of Europe of 5 May 1949 determines that resolutions of the Committee of Ministers relating to enumerated ‘important matters’ require ‘the unanimous vote of the representatives casting a vote, and of a majority of the representatives entitled to sit on the Committee’. To mention a third example, Art. 26 Andean Subregional Integration Agreement (‘Cartagena Agreement’) of 1969 provides that the Andean Community Commission shall adopt its decisions by affirmative vote of the absolute majority of the member countries, but that in matters listed in Annex I to the Agreement the Commission shall adopt its decisions ‘by the affirmative vote of the Member Countries with no negative votes being cast’. In the cases listed in Annex II to the Cartagena Agreement, General Secretariat proposals ‘shall be approved with the affirmative vote of the absolute majority of the Member Countries, provided that no negative vote is cast’ (Art. 26 (b) Cartagena Agreement).
2. The Right of Veto in the Proper Sense
21 A right of veto in the proper sense is constituted by a constitutional rule of an organization—which generally adheres to a system of majority voting—entitling one or more Member States to prevent a certain decision from being taken.
22 By way of example, we mention Art. 12 Convention concerning the Regime of Navigation on the Danube of 18 August 1948 (‘Danube River Convention’; Danube River) which provides that decisions of the Danube Commission regarding ‘principal works called for in the interests of navigation’ shall be taken by a majority vote of all members of the Commission ‘but without outvoting the State of the territory on which the works are to be carried out’.
23 A unique form of veto was given to the Grand Duchy of Luxembourg in the framework of the 1956 Moselle Convention. To finance and construct the canalization of the Moselle, a company with limited liability, incorporated in Germany, was established, the Société Internationale de la Moselle [GmbH]. According to the statute of the company, decisions of the supervisory board (Aufsichtsrat, Conseil de Surveillance) and the shareholders’ meeting (Gesellschafterversammlung, Assemblée Générale) are to be taken by a two-thirds majority. However, if a decision directly affects the territory of Luxembourg, this decision requires the assent of the Luxembourgian members of the board or of the Luxembourgian shareholders, respectively (see Art. 15 (3) and Art. 21 (1) Annex II to the Moselle Convention).
E. Concluding Observations
24 An undifferentiated condemnation of the veto as an element of the voting system of international organizations as ‘undemocratic’, ‘unfair’, or incompatible with the principle of sovereign equality appears to be unfounded. There is no rule of international law that would generally prohibit the introduction of a right of veto for particular Member States into the law of an international organization. As sovereign entities, States forming an international organization are free to agree on a provision of the founding treaty which confers such a right on particular Member States, to the detriment of others, in the same way as they are free to agree on majority voting or a system of weighted voting.
25 Further, conferring a right of veto on certain States may be the only way of inducing them to join a particular organization and, thus, to achieve the goals pursued with the establishment of the organization. ‘By giving a right of veto to the states whose cooperation is essential, the advantages of decision-making by unanimity can partly be combined with those of decision-making by majority vote’ (Schermers and Blokker 560).
26 It is therefore necessary to judge carefully each individual case of a veto power on its own merits. While it is true that the principle of sovereign equality suggests an equal voting power of all Member States of an international organization or conference, there may be good reasons which support a limitation of that equality in the form of a veto given to certain States whose co-operation can only thereby be assured. However, because of its exceptional character a right of veto should only be conferred on a State, and maintained over the course of time, to the extent necessary to the performance of functions of the organization in question.