This is the body of rules that are binding on states and other subjects of international law, in particular international organizations, in their relations with each other.

Closely related to the concept of sovereignty of states, the norms of international law are binding because states consent that they should be. The expression of this consent appears from the actual practice of states in the case of customary international law and from ratifications in the case of treaties, to which the concept of pacta sunt servanda applies. This asserts that treaties are binding on the parties to them and must be executed in good faith. To the extent that the rules of international law influence the behaviour of states in world politics, they are a social reality, thus constituting an institution of international society, or proof of the existence of an international community.

There are various sources of international law. These sources are listed in Article 38(1) of the Statute of the International Court of Justice as follows:

International conventions or treaties, which are binding only on the parties thereto.International custom, which describes the rules derived from the general practice, based on the perception of a legal requirement, among states in international relations; they are, with few exceptions, binding on all states.General principles of law, such as good faith, recognized by civilized nations, which are also binding on all states.Judicial decisions, for example of international tribunals, and the writings ofeminent scholars; these help to determine the existence and the interpretation of these several types of binding rules.The issues of global health governance and international law are closely related. Much, but not all, international law is limited by the absence of an international authority that can enforce it, so compliance is voluntary.

International laws that relate to public health date back to the 1850s, when the first treaties on the control of infectious diseases were signed. A specific body of law on communicable disease control has emerged since then (which includes the International Health Regulations). There has long been recognition that laws are a fundamental part of public health and global public health. Areas that relate to public health include:

International trade laws, which govern the trade in pharmaceuticalsInternational human rights law, which aims to protect the human rights of individualsInternational environment law, which addresses environmental problems that havean impact on global health problemsInternational humanitarian law, which aims to protect the health of combatants and non-combatants in times of armed conflict.More recently, it has been suggested that the sources of international law may not be confined to those defined by the Statute. Soft law, for instance non-binding resolutions of international organizations, are also cited as credible sourcesbecause they consist of rules that are not actually binding, but that are expected to be and usually are complied with, and that may gradually harden into binding law. As a result, the relevance of international conventions to public health, such as the Framework Convention on Tobacco Control, and rules formulated by international organizations such as WHO's International Health Regulations, has increased.

An international regime refers to a convergence of thinking and commitments among a group of states on a particular issue. It covers acceptance of a set of rules and regulations, or acceptance that such rules are needed. Examples of international regimes include the Codex Alimentarius and the Breast Milk Substitution Code.