By Maria Theresa Dojillo,  Maria Lalyn Escalona, Therese Mikaela Maravilla, and Charlene Mae Rio,


International law is a system of treaties and agreements between nations that governs how nations interact with other nations, citizens of other nations, and businesses of other nations. International law typically falls into two different categories.

Public is international in nature.  It is a law of a sovereign over those subjected to his sway.  “Public international law” is traditionally defined as the law between sovereign nation-states, hereinafter, states, especially within the context of the laws of war, peace and security, and protection of territories. While these concerns of international law remain paramount among states today, the classic definition of public international law has expanded to include a more diverse group of subjects and a broader scope of activities. 

It is a body of rules and principles that are recognized as legally binding and which govern the relations of states and other entities invested with international legal personality. It concerns the relationships between nations. These include standards of international behavior, the laws of the sea, economic law, diplomatic law, environmental law, human rights law, and humanitarian law. Some principles of public international law are written, or codified in a series of treaties, but others are not written down anywhere. These are known as customary laws, and nations consent to them by doing nothing.

Since most international law is governed by treaties, it’s usually up to the individual nations to enforce the law. However, there are a few international organizations that enforce certain treaties. The most notable example is the United Nations, which has 192 member states.

International law’s distinguishing feature – which sets it apart from an institution, practice, or political agreement – is its acceptance in principle as binding. Public international law comprises a set of binding rules among states. Increasingly we can find instances in which such rules govern individuals such as international criminal law and some aspects of the laws of war. Only states or in some cases, organizations of states can enter into international legal agreements, or treaties. This binding state-to-state quality distinguishes international law from the broader concept of international institutions, which can include non-binding practices and which, many would agree, can also include rules and principles devised by non-state actors.

International Law Theories

Command Theory. In the view of John Austin, a renowned legal philosopher, law consists of commands originating from a sovereign and backed up by threats of sanction if disobeyed. In this view, international law is not law because it does not come from a command of a sovereign. Neither treaties nor custom come from a command of a sovereign. This theory, however, has generally been discredited. The reality is that nations see international law not as commands but as principles for free and orderly interaction.

Consensual Theory. Under this theory, international law derives its binding force from the consent of states. Treaties are an expression of consent. Likewise, custom, as voluntary adherence to common practices, is seen as an expression of consent. However, there are many binding rules which do not derive from consent.

Natural Law Theory. The natural law theory posits that law is derived by reason from the nature of man. International law is said to be an application of natural reason to the nature of the state-person. Although the theory finds little support now, much of customary law and what are regarded as generally accepted principles of law are in fact an expression of what traditionally was called Natural Law.

Some dissenters, however, see no objective basis for international law. They see international law as a combination of politics, morality and self-interest hidden under the smokescreen of legal language.

Sources of International Law

The task of ascertaining what the laws are in the domestic sphere is a relatively simple matter. Domestic laws are found in statute books and in collections of court decisions. It is an altogether different matter with international law. In the absence of a centralized legislative, executive and judicial structure, there is no single body able to legislate and there is no system of courts with compulsive power to decide what the law is nor is there a centralized repository of international law. Thus, there is the problem of finding out where the law is. This problem is exacerbated by the anarchic nature of world affairs and the competing sovereignties. Nevertheless, international law exists and there are sources where, with some effort, the law can be found.

Sources are often classified into formal sources and material sources. Authors, however, differ in defining these concepts. Formal sources can refer to the various processes by which rules come into existence. Thus, for instance, legislation is a formal source of law. So are treaty making and judicial decision making as well as the practice of states. Material sources, on the other hand, are not concerned with how rules come into existence but rather with the substance and content of the obligation. They identify what the obligations are. In this sense, state practice, United Nations Resolutions, treaties, judicial decisions and the writings of jurists are material sources in so far as they identify what the obligations are. They are also sometimes referred to as evidence of international law.

The doctrine of sources lays down conditions for verifying and ascertaining the existence of legal principles. The conditions are the observable manifestations of the wills of States as revealed in the processes by which norms are formed — that is, treaty and state practice accepted as law. The process of verification is inductive and positivistic. It is the process of finding what laws the states themselves have created and what laws they are willing to place themselves under. It is a manifestation of the fact that international law is characterized by individualism.

It is interesting, however, that the most widely accepted statement of the sources of international law, that is, Article 38(1) of the Statute of the International Court of Justice, does not speak of sources. Rather, Article 38 is primarily a directive to the Court on how it should resolve conflicts brought before it.

Article 38 provides:

The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:

a. international conventions, whether general or particular, establishing rules expressly recognized by contesting states;

b. international custom, as evidence of a general practice accepted as law;

c. the general principles of law recognized by civilized nations;

d. subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law.

· This provision shall not prejudice the power of the Court to decide ex aequo et bono, if the parties agree thereto.

Article 38 is a declaration by states that these are the laws under which they are willing to be bound. Thus, another statement of sources is the Restatement (Third) of Foreign Relations Law of the United States which says:

A rule of international law is one that has been accepted as such by the international community of states

a) in the form of customary law;

b) by international agreement; or

c) by derivation from general principles common to the major legal systems of the world.

· Customary international law results from a general and consistent practice of states followed by them from a sense of legal obligation.

· International agreements create law for the states parties thereto and may lead to the creation of customary international law which such agreements are intended for adherence by states generally and are in fact widely accepted.

· General principles common to the major legal systems, even if not incorporated or reflected in customary law or international agreements, may be invoked as supplementary rules of international law where appropriate.

Basis of Public International Law are the three (3) schools of thought, which explains why the rules of international law are binding.

The Naturalist says that Public international law is a branch of the great law of nature – the sum of those principles which ought to control human conduct, being founded on the very nature of man as a rational and social being. Public international law is binding upon States.

The Positivist says that the basis is to be found in the consent and conduct of the States.  Tacit consent in the case of customary international law.  Express consent in conventional law.  Consent is presumed in the general law of nations. Groatians or Eclectics accept the doctrine of natural law, but maintained that States were accountable only to their own conscience for the observance of the duties imposed by natural law, unless they had agreed to be bound to treat those duties as part of positive law.


This study on the evolution of Public International Law between the State and other entities is conducted to achieve the following objectives:

  1. To expand the knowledge on the complexities of the history of Public International Law.
  2. To understand the current operations of Public International Law with relation to the State and other entities.


This study focuses on the complexities of past and present operations of Public International Law. This study is only limited to finding out the operations of Public International Law between the State and other entities. This research does not discuss other aspects of Public International Law.


General principles of law historically derive from state practice and possess a less definable character as compared to other sources of international law. Classic examples of principles are equity, comity, fairness, and good faith. Like customary international law, general principles develop over time and their identification, appraisal, content, ranking, enforceability, and applicability are the subject of different scholarly and judicial perceptions. (Bassiouni, M.C., 1989. A Functional Approach to General Principles of International Law, Michigan Journal of International Law, Vol. 1, pgs. 768- 818)

As characterized in 1963 by Marjorie Whiteman, a former US legal advisor:

“While international law is comparatively clear and definite in many of its aspects, in others it is unclear and uncertain. It may be that a particular norm or principle, far from being its zenith, may be either in its ascendancy or in its descendancy as international law. Further, the degree of acceptance of a particular practice may vary within a particular period. “ (Whiteman, 1963. Digest of International Law, Vol. 1, Preface III)

The traditional definition of international law has also broadened in scope to include additional topics or branches of international law. The body of human rights law did not formally develop until after World War II. Recognition of international organizations having legal personality and capacity to enter into treaties is reflected in the 1986 instrument.

Newer and emerging areas of international law often involve an intersection between two or more branches of international law, for example, international humanitarian law impacts the protection of cultural property and environmental law.

Several unique features distinguish international law research from researching law of domestic legal systems. These features relate to non-hierarchical legal authority, the interaction of international and national law, and language considerations.

Non-Hierarchical Authority – Legislative and Judicial

The absence of a central legislative body and hierarchical judicial authority is unique to international law. The largest international organization is the United Nations (UN) which currently has 193 member states. Resolutions and declarations of the United Nations and other international organizations are non-legally binding instruments and do not create legal obligations for States.

The jurisprudence of international law consists of case law from a variety of international courts and tribunals. With the exception of courts like the World Trade Organization (WTO) arbitral chamber and appellate courts or, the appellate character that may exist in courts of regional institutions like the European Union (EU), there is no high court in international law. The International Court of Justice (ICJ), the judicial organ of the United Nations, is named the World Court; however, it is not a hierarchical or appellate court. The decisions of the International Court of Justice are only binding on the states that have agreed to its jurisdiction. Still, ICJ decisions, like decisions of other international and national courts, may be consulted or referenced as persuasive authority.

International Law and National Law

A unique dimension of researching international law relates to the way in which national legal systems incorporate, implement, or apply international law in their domestic or municipal law. Thus, in addition to researching resources of international law, research in national law materials such as legislative acts and judicial decisions may be necessary.

Multilateral Perspectives for Multilateral Instruments

Given the multilateral participation of member states in international law, resources and documents may be available in selected languages only. In the event the researcher is met by language limitations in accessing certain materials, translations and works from different legal systems and perspectives must be identified, if available and affordable.

French has historically been the dominant language used in international relations and diplomacy and also, documents of international law. Since World War II, English language versions or translations became more commonplace. Translations for multilateral instruments deposited with the UN are available in Arabic, Chinese, English, French, Russian, and Spanish.

Initial Search Strategy

One general note that applies to researchers new to a particular area of international law is the role of secondary resources in the research process. Even in an increasingly internet-dominant research environment, consulting authoritative texts and other secondary resources continues to be an important and time saving step for several reasons. Secondary resources: 1) provide a solid, foundational understanding of the subject, 2) identify the principal instruments, significant court decisions, and other relevant documents in the topic area along with corresponding citation information, 3) provide discussion and analysis of known customary law, legal principles, and norms, 4) introduce and define important terms and concepts, and, 5) allow the researcher to perform online searches more effectively by constructing searches using known terms of art and alternate search terms.


This study on Public international law used the descriptive-comparative research design since the researchers compared the former and current operations between the State and other entities. Comparative research design is the analysis of data which compares two or more concepts aiming to identify and analyze the similarities and differences of the groups being compared. This study compares two periods of Public International Law to further understand the similarities and differences among the compared periods.

The researchers applied data from previous studies and other literary works to further explain the topic and provide conclusions. The gathered data were used to answer the objectives of the study. The group’s collaborative discussion about the resources obtained were also beneficial to the findings of the study.


In the post-Cold war era, state creation and the practice of international law of statehood are influenced by the political system. In the pre-1990, UN Charter era, the process of state creation was shaped by certain human rights norms, violations of which were capable of rendering a state creation illegal under international law. However, in this period, the nature of an entity’s political system did not play any role in the process of the emergence of new states.

During the post-1990 years, the World had witnessed an ongoing and almost obvious process whereby the international legal order shifted towards a more robust, more elaborated and more efficient system of legally binding norms (rather than mere political ‘expectations’). This development extended to both, pre-existing and almost traditional, areas of international law as well as to somewhat more recent areas of international law. In different circumstances, international environmental law, international trade law or international criminal law either saw the development of new substantive rules, or the creation of new organizations to enforce those rules. (Zimmermann A., 2018)

Today, international law, in its transformed or globalized version, governs all sorts of relations, including those implicating states, regional bodies, NGOs, trade organizations, commercial actors, and private individuals. (Barry E. Carter & Philip R. Trimble, International Law 2 – 3rd ed. 1999) It spreads into legal fields such as environmental law, labor law, trade regulations, antitrust, health, and insurance law. Non-state actors play increasingly important roles in such fields, including regional organizations, specialized bodies such as trade organizations, NGOs, and private individuals. Finally, private individuals exercise increasing influence in the international legal field. Private parties can now enter into investment treaties with state parties; moreover, they can sue state parties in specific tribunals for breaches of such investment relations.


The material sphere of validity of the International legal order is unlimited. That being so, it is impossible to define the concept of International law by its object, i.e., by the matters to which its norms refer or which they regulate. In an era of increasing globalization, international law forms a critical part of the framework that promotes sustained cooperation among states. While skeptics may continue to question the scope and impact of international law as real law, simple observation should quickly provide strong evidence that states do regard international law as an important factor in their everyday relations with one another.

International law now plays a different role in today’s globalized world. While a century ago, international law was only meant to govern relations among states, this is no longer true. International law has not only witnessed a proliferation of legal norms, but also an expansion in the number of international legal organizations. ( Dunoff et al., supra note 35, at 27 )

There is no doubt that observance of International Law poses some fascinating and sometimes, daunting jurisprudential questions. There are differences of opinions about its legitimacy, efficacy and compliance. Ensuring them has proved hard over decades. Combined with International Relations, International Law had remained an erratic and unpredictable issue.

Thus, it is no longer that international law represents a body of law that solely governs relations among states; on the contrary it is a complex web of regulations, treaties, customary norms, and codes of conduct that shapes relationships among state as well as non-state actors along horizontal and vertical axes of power.


Command Theory – A theory in international law that states, laws consists of commands originating from a sovereign and backed up by threats of sanction if disobeyed.

Consensual Theory – A theory that international law derives its binding force from the consent of states.

Doctrine of Sources – Lays down conditions for verifying and ascertaining the existence of legal principles.

Domestic Law – The law or legal system established within a state to govern events, transactions, and persons within or having a connection to that state; also internal, municipal, national, or local law/legal system.

ex aequo et bono – a Latin term which means what is just and fair or according to equity and good conscience.

International Agreements – Formal understandings or commitments between two or more countries. 

International Law – The law which regulates the intercourse of nations; the law of nations.

Natural Law Theory – A theory in international law that states, law is derived by reason from the nature of man International law is said to be an application of natural reason to the nature of the state-person.

Public International Law – The body of rules which control the conduct of independent states in their relations with each other.

Treaty – An agreement, league, or contract between two or more nations or sovereigns, formally signed by commissioners properly authorized, and solemnly ratified by the several sovereigns or the supreme power of each state.

United Nations – An organization started by the allied powers in World War II for the stated purposes of preventing war, providing justice and promoting welfare and human rights of peoples.


Statute of the International Court of Justice

Cherif Bassiouni, A Functional Approach to General Principles of International Law, Michigan Journal of International Law, Vol. 1, pgs. 768- 818 (1989-1990)

Whiteman, Digest of International Law, Vol. 1, Preface III (1963)

Dunoff et al., supra note 35, at 27


The researchers are excited to share their ideas on the conceptualization of this research. This study has been made possible by the guidance, cooperation, and participation of the following:

A heartfelt gratitude to our Almighty God for His divine, wisdom and unfailing love.

To our beloved and patient professor, Atty. Jocelle Batapa for teaching and guiding us throughout this study.

Most especially to our dear parents for their patience and support in making this research paper possible.


The researchers are First Year Juris Doctor students from the University of St. La Salle College of Law.

Maria Theresa Dojillo

Maria Lalyn Escalona

Therese Mikaela Maravilla

Charlene Mae Rio

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