For those who believe that the “general principles of law” constitute a third source of international law, which is not limited to the jurisdictional system of the International Court of Justice in The Hague, the principle of the inviolability of treaties is a general principle of law.34 It is found in the foro domestico, as we have seen: in all countries. This is one of the most important general principles of the law governing relations between nations. Without the powerful instrument of the treaty, no international law is possible.35 Since this author is a proponent of the carefully adapted application of natural law to international relations, applied with social necessity in mind, the idea that the sanctity of treaties is based on a general principle of law seems particularly evident.36 Sovereignty can be seen as the ultimate authority that flows from and depends on statehood. At the international level, while international organizations perform certain functions normally associated with States, traditionally only States are called sovereign. This may now change, as some argue that the European Union, for example, has some kind of sovereignty, with its member states now sovereign in a different, “late” or post-national sense (MacCormick 1993 [2006:4, 16]; Walker, 2003, p. 9). At the national level, the situation is more complicated, as more subjects – from monarchs to parliaments, from individuals to peoples – have been considered sovereign at different times and in different ways (Verdirame 2016). Legal philosophers who write about international law have often assumed that contract and custom ultimately depend on state consent. Ronald Dworkin, for example, believed that the idea that a state is subject to international law only to the extent that it has agreed to be bound by it reflects what “seems to be generally accepted today by practitioners and scholars of international law” (Dworkin 2013: 5). Indeed, the consensual presentation of international law also enjoys broad support among international lawyers. In a 1996 case, the International Court of Justice described consent, along with sovereignty, as “the very foundation of international law” (ICJ 1996: para. 21).

This chapter deals with international law, focusing on the extent to which it was allowed to invade local English law and the conditioning of British leadership in foreign affairs. There is another fundamental concept that must be taken into account in explaining the role of sovereignty in modern international law: self-determination. Self-determination is mentioned prominently in Article 1(2) of the Charter of the United Nations as one of the purposes of the United Nations. In international law, self-determination is a right of all peoples, defined identically in the Charter and the International Covenants on Civil and Political Rights (1966) and on Economic, Social and Cultural Rights (1966) of the United Nations, as the right to “freely determine their political status and freely pursue their economic, social and cultural development”. the rule of law applies equally to all States and international organizations, including the United Nations and its principal organs. (United Nations General Assembly Resolution 67/1, 24 September 2012, paragraph 2) An important set of normative issues concerns the relationship between international organizations and political and individual freedom. Some argue that while the transfer of sovereign functions to international organizations may be justified on a number of moral and political grounds, it cannot reach the point where it endangers human rights or undermines self-government – these limits are necessary to preserve the liberal character of the international order (Verdirame 2013). It is a Latin term that means that agreements must be respected. It exists in both civil and international law. In international law, this means that any treaty is binding on the parties and must be performed in good faith. Good faith is a sincere intention to fulfill obligations without malice. The parties must fulfil their promises and obligations to the best of their ability.

This is subject to certain conditions, which we will discuss later in this article. We have described above the pacta sunt servanda rule as a general principle of law found in all nations. It follows that this principle applies in exactly the same way whether in contracts between States or in contracts between States and private companies. Irrespective of whether, in the case of Verdross54, a State`s contracts with a foreign company for the purpose of awarding concessions are regarded as quasi-international agreements or whether they are given a different character, the principle of the inviolability of treaties must always be applied. We also discussed the scope of the principle and stated that States bound by such a principle must have given their consent to be party to such a treaty. Many contemporary authors focus on the European Union, which has been described as “supranational” rather than international, given the direct primacy of EU law in national legal spheres (Neyer & Wiener 2011a; van Middelaar 2013). Whether supranationalism is a way of attributing sovereignty to the European Union or of rethinking the legal order in a post-sovereignist and cosmopolitan sense is an open debate (Eriksen 2011). For others, the process of European integration poses a challenge to the modern liberal constitutional sense of sovereignty, as defined by “overall competence and responsibility for the common good of peoples united in a community… and the transfer of regulatory power over the state economy risks paving the way for “a fragmentation of concern for the common good” (Böckenförde 1997).

For example, Georg Jellinek (1851-1911), whose influence on international law cannot be overstated, based the validity of international treaties on the self-imposed obligation of states: The balance between cosmopolitan international law (i.e. the law that binds all states) and national sovereignty is explored in John Rawls` Law of Peoples (Rawls 1999; see also Wenar 2008 [2021]). Rawls himself uses the term “sovereignty” or “state” not in reference to societies that are members of his “society of peoples”, but because he associates “sovereignty” with an absolutist conception and considers “states” as a claim to this sovereignty. In contrast, his theory advocates a more limited notion of sovereignty for “well-ordered peoples.” These peoples enjoy both legitimacy vis-à-vis their own citizens and full international prestige in the society of peoples, which includes immunity from interference. Legal philosophers disagree on the correct characterization of the rule of law, as their different viewpoints occupy different points along a spectrum ranging from “thin” or formal-procedural representations to increasingly “thick” or substantial representations (Waldron, 2016; Tasioulas 2020a). They identify “thick” rule of law relationships with something close to all the formal, procedural, and substantive requirements that a good law should meet; or any requirement that constitutes legitimate law (Beyleveld & Brownsword 2007); or all demands for political justice (rights) relating to the law (Dworkin 2011); or some favoured a comprehensive set of legally relevant wishes, such as respect for democracy and human rights (Bingham 2010; Annan, 2004).