This chapter covers the international law governing the use of force between states – the jus ad bellum. This is in contrast to the jus in bello – the law of armed conflict, or international humanitarian law – which regulates the conduct of hostilities once under way (see Chapter 11). Since at least 1945 the use of force by states has been prohibited, except in self-defence or when authorised by the United Nations Security Council. This chapter analyses the prohibition, the two exceptions, and the controversial issue of humanitarian intervention and its close relative, the ‘responsibility to protect’.

Public international law is a worldwide legal system which regulates the conduct of states (countries) and other actors, both in their international relations and within states’ territories. It governs many areas, such as sovereignty over territory; rights and responsibilities at sea; environmental protection; human rights and the suppression of international crimes; trade and investment; the use of military force; responsibility for breaches of the law; and the settlement of disputes. This chapter introduces the main features of public international law, including its history, sources and purposes. It outlines what the law regulates, who has rights and bears obligations under it, and how it is implemented and enforced. The chapter then considers jurisprudential debates about the nature of public international law as ‘law’ and the reasons for compliance with it, and concludes with discussion of some key critical theories.

All states have an obligation to settle disputes peacefully in accordance with arts 2(3) and 33 of the Charter of the United Nations (‘UN Charter’), and the purpose of this chapter is to provide an introduction to the methods for the settlement of international disputes. It begins with an overview of international dispute settlement, including a discussion of the concept of a ‘dispute’, and the distinction between political and legal disputes. It then traces the evolution of the obligation to settle disputes peacefully through its broad phases: the 1899 and 1907 Hague Conventions for the peaceful settlement of international disputes, and the creation of the Permanent Court of Arbitration; the Covenant of the League of Nations of 1919, and the creation of the Permanent Court of International Justice (‘PCIJ’); and the Kellogg–Briand Pact of 1928, and the UN Charter of 1945. The chapter then considers the various methods of international dispute settlement, beginning with the diplomatic methods (negotiation, fact-finding and inquiry, the use of ‘good offices’, mediation, and conciliation) before turning to the adjudicatory forms of dispute settlement.

International environmental law (‘IEL’) began to emerge as a distinct subdiscipline of international law in the 1970s. Since then, it has assumed critical importance in helping to maintain the ecological systems upon which all life on planet Earth depends. It is continuing to develop and is relevant to all states and communities, affecting a wide range of human activities and concerns. This chapter briefly traces the history of IEL and sets out some recent institutional and policy developments, including the United Nations Environment Assembly and the UN Sustainable Development Goals. It also looks at concerted attempts to fill gaps in the field. Given the vastness of the subject matter, the chapter does not purport to be a comprehensive or in-depth analysis. It addresses the main organising principles of IEL, both established and emerging. It provides an overview of treaties (also referred to as multilateral environmental agreements or ‘MEAs’) in several key subfields, including regimes addressing the atmosphere, transboundary pollution, chemicals and wastes, biodiversity, and land degradation. It also includes a case study on world heritage and its implementation in Australia.

International economic law is an umbrella term with no fixed meaning. At its broadest, it covers all aspects of economic relations between states, including regulation of the conduct of individuals, corporations and international organisations. A narrower meaning is ‘the segment of public international law directly governing – rather than merely affecting – economic relations between States or international organizations’. The field also embraces governance arrangements, such as the World Bank, International Monetary Fund, and World Trade Organization, as well as the many UN and regional bodies that advance economic development. As space does not permit a discussion of all these aspects, this chapter focuses on two important areas: international trade law and international investment law. International trade law is the body of law, mainly treaty based, that governs the terms on which states permit the trade in goods and services across their borders.

To explain the law of state responsibility and diplomatic protection, it helps to distinguish between primary rules and secondary rules. The primary rules of international law provide that certain acts or omissions are unlawful – for example, the law on the use of force would be considered primary rules of international law, a breach of which would be an internationally wrongful act. When those primary rules are breached, it is the secondary rules – the law of state responsibility – that come into play, to determine inter alia the consequences of that initial wrongful act, whether the wrongful act was committed by a state (thereby entailing that state’s responsibility), and what action the ‘wronged state’ may take in reply. The rules on state responsibility cover wrongful acts committed against another state, as well as certain wrongful acts committed against nationals of the state, including corporations; the law of diplomatic protection solely concerns how a state may raise a claim against another state for a wrong committed against one of its nationals, rather than against the state itself.

The law of the sea, one of the oldest areas of international law, is now substantially codified in the 1982 United Nations Convention on the Law of the Sea (‘UNCLOS’), the ‘constitution for the oceans’. UNCLOS ushered in the modern law of the sea, providing a comprehensive regime for maritime zones, navigational rights and freedoms, fishing and other uses of the world’s oceans that cover approximately 70% of the Earth’s surface. As an island country with extensive maritime zones, Australia has a major stake in the law of the sea and has been actively involved in its development and implementation. Australia was one of the original signatories to UNCLOS and ratified it in 1994, the year it entered into force generally. The central issues of concern for the law of the sea have traditionally been the extent of maritime jurisdiction and navigational rights. However, a much broader range of matters is addressed in contemporary law and practice, from sustainable fisheries management through to mining of the deep seabed beyond national jurisdiction. There are also major new challenges on the horizon – none more so than climate change.

International human rights law (‘IHRL’) provides minimum standards which states must observe in their treatment of individuals under their jurisdiction. In this respect, it differs from many other areas of international law which focus on regulating international relations between states. The human rights recognised in international instruments are considered to be fundamental rights which all human beings are entitled to enjoy, regardless of their personal circumstances or the state in which they reside.

The starting point for discussion and analysis of the sources of international law is almost invariably art 38 of the Statute of the International Court of Justice (‘ICJ Statute’), the International Court of Justice being the primary judicial organ of the United Nations. Article 38 lists the sources of international law as comprising treaties, custom, general principles of law, and – as subsidiary means for determining the law – judicial decisions and academic writing. However, in the 75 years since the adoption of the ICJ Statute, newer sources of legal obligation have emerged for the international community. These often involve non-state and intergovernmental actors in their creation. This chapter explores both the traditional and newer sources of international law and assesses how they are adopted and created.

Before the 20th century, most rules of international law were in the form of customary international law. Since then, the increased complexity of international relations and rapid international development have led to a substantial growth in the number and diversity of treaties. Article 38(1)(a) of the Statute of the International Court of Justice (‘ICJ Statute’) recognises treaties as a (material) source of international law by referring to ‘international conventions, whether general or particular, establishing rules expressly recognized by the contesting states’. Treaties now regulate trade, communications, environmental protection, military cooperation and defence, and human rights, to name but a few of the myriad topics. International environmental law, for example, is almost entirely governed by treaties, and international trade, investment and communications ‘are unimaginable without treaties’. The main rules in the law of treaties are contained in the 1969 Vienna Convention on the Law of Treaties (‘VCLT’), which governs treaty relations between states and is the focus of this chapter.

Speech is normally used for verbal interaction between at least two persons, called interlocutors. Researchers have measured rate of information transfer by speech across languages and have found a relatively constant value across languages. Spoken language is very different from written language in a number of important ways. Speech is perceived by hearers based primarily on the acoustic information contained in the speech signal, but modified by a number of factors, including top--down processing. Perception is made more complex by factors such as the necessity of segmenting and variance in the signal caused by individual differences and conditions of the speech environment. Speaker normalization is required by the hearer. The ear and hearing mechanism play an important role in speech perception. Rapid pressure variation of sound is converted to fluctuations in the viscous fluids of the inner ear or cochlea. This conversion occurs through the middle ear in which the principle of the lever, and the principle of collecting energy over a large area and concentrating it, play roles.

Speech consists of sound waves that propagate in the air from talker to hearer. Sound waves consist of rapidly changing pressure within the medium, normally air in the instance of speech. If the variations of pressure are regular, then the sound has a tonal quality. Most, but not all, speech sounds have this tonal quality. Sound amplitude relates to the amount of energy and is perceived as loudness. The speed of pressure variation is called frequency and is perceived as pitch. Individual sound waves combine additively, creating complex sound waves. Acoustic analysis of speech creates spectrograms, giving a visual representation of the original sound. In certain conditions, such as the interior of the vocal tract, sound reverberates in a self-additive way, giving rise to cavity resonance. The frequencies of this resonance can be modified by adjustments in the position of the speech articulators, creating different speech sounds, which occurs through the source--filter theory.