International law, also called public international law or law of nations, is the legal body describing rules, norms, and standards that apply between sovereign state and other entities which are legally recognized as international actors.

International Law
Each country in the world formulates laws to govern the society in efficient manner and ensure peace and security. Similarly, at the international level, when countries come together at a common platform to formulate law that governs intercourse between them, it is referred as international law.

According to Encarta Encyclopedia:
International law is a body of laws, principles, rules and standards that govern nations and other participants in international affairs with one another.

In other words:
International law is the law of the international community. The term 'International Law' was used by Jeremy Bentham in 1780. The expression Law of Nations is synonymous with the term international law. It acts as a legal framework at global level to ensure stable and organized international relation.

Definitions of International Law
According to Fenwick:
It is the body of rules accepted by the general community of nations, as defining their rights and the means of procedure by which those rights may be protected or violation of them is redressed.

According to J.G. Starke:
It is that body of law comprised of greater part of its principles and rules of conduct, which States feel themselves bound to observe and therefore do commonly observe in their relations with each other.

According to Prof. L Oppenheim:
Law of nations of international law is the name for the body of customary and conventional rules which are considered legally binding upon civilised states in their course with each other.

According to J.L Brierly:
The law of nations of international law may be defined as the body of rules and principle of action, which are binding upon civilized states in their relation with one another.

According to Philip C Jessup:
International law or the law of nations must be defined as law applicable to States in their mutual relations with other States. He adds further that international law may also be applicable to certain inter-relationships of individuals themselves, where such inter-relationship involves matter of international concern.

According to Torsten Gihl:
The term international law means the body of rules of law, which apply within the international community or society of states.

According to Gray:
International law or the law of nations is the name of a body of rules which according to their usual definition regulate the conduct of States in their intercourse with each other.

According to Hall:
International law consists of certain rules of conduct which modern civilized States regard as binding on them in their relation with one another with a force comparable in nature and degrees to that binding the conscientious person to obey the laws of his country and which they regard as being enforceable by appropriate means in case of infringement.

Objectives of International Law

1. To ensure peace and security in the world.
2. To resolve any dispute in peaceful manner.
3. To co-operate with each other, to strive for the better and brighter future of human kind.
4. Disarmament of weapons of mass destruction especially nuclear and building trust between nations through confidence building measures.
5. Taking collaborative effort to solve global problems such as terrorism, climate change, refugee crisis etc.
6. International law emphasizes on implementation of international treaties and conventions in right manner.

Nature of International Law
International law is quite dynamic in nature as it has multiple stakeholders. So, it's not easy to outline nature of international law. Jurists have different opinions regarding nature of international law.

It's nature can be understood through following given points:

1. It is not easy to formulate principles, rules and regulations, methods, etc., of international law.
2. Principle of reciprocity act is a basis of international law.
3. The framework of interaction between nations is also established by the international law.
4. Municipal law of nations implements the provisions of international law in their respective jurisdiction.
5. Collective action is taken by countries when any country violates the principles of international law.
6. International law provides for peaceful resolution of disputes and discourage military or economic sanction route.
7. There are different sources of international-law such as custom, treaty, charters etc.
8. States are allowed to implement international law in their territory according to their wishes.

Evolution of International Law
International law is not just a result of few treaties of 19th and 20th centuries but its origin can be traced back to ancient times. Peace treaties between the Mesopotamian city of Lagash and Umma are considered as beginning of international law. The concept of governance and international relations were developed by the Greeks, which laid down the foundation of the international legal system. The concept 'Jus Gentium' (Law of Nation) was evolved during the reign of the Roman empire, which defined and governed the relation between foreigners and Roman citizens and the status of foreigners living in Rome. Later, development of concept of Natural Law emphasized that certain rights are inherent to all humans, which helped in widening the scope of international law.

Present day modern international law was evolved during 15th century and was mainly developed in European continent. Renaissance in Europe has played significant role in the development of international law. Hugo Grotius is considered as most eminent personality in the field of international law. He had articulated international order that consist of a 'Society of States' which should be governed by the law's, mutual agreement and custom rather than by force and or warfare.

Two schools of international law, the naturalist and the positivist were established, following the footprint of Hugo Grotius. Enaction of Westphalian System is major landmark in the field of international law. It acknowledged the concept of independent sovereign entities known as 'Nation State'. International law mainly came into limelight in the 19th and 20th centuries.
Development of International Law (During 19th and 20th Centuries)

During 19th and 20th centuries, international law got its formal shape. Various pacts and treaties were signed in this period which finally concluded in the formation of United Nation. Various treaties, declarations, conferences are as follows:
Congress of Vienna (1815)
Congress of Vienna is known as watershed moment in the evolution of international law. It is also referred as Vienna Congress, held in 1815. It was chaired by Klemen's Von Metternich, an Austrian statesman. It was attended by ambassador of European states with the objective to provide a long-term peace plan for Europe. Solving critical issues aroused from the French Revolutionary War and the Napoleonic War were main agenda of the Congress. It laid down the international rules such as rules with regard to International River, categorization of diplomatic agent etc.

Paris Declaration (1856)
It is another important landmark in evolution of international law. In this declaration, 55 nations agreed on the diplomatic policy related with the Maritime Law. This declaration also laid down the rules relating with the naval warfare.

The main principle that evolved in it was to prohibit attack on undefended people and before sinking enemy ship, attempt should be made to save the life of the crew. It was codified by France and Great Britain.

Three agreed principles of the declaration were no privatizing, effective blockade and free ship make free goods. This declaration redefined the relationship between belligerent and neutral nations. It paved the new rules for the navigation in high seas.

Geneva Convention (1864)
It formulated rules and regulations for the protection of victims of armed conflict and people involved in providing care to them. The first Geneva Convention treaty was adopted in 1864, which was reframed and amended in 1906, 1929 and in 1949. Overall, there are four treaties of Geneva Convention. At present, the International Committee of Red Cross mainly sees the implementation of Geneva Convention. Killing of wounded soldiers were prohibited in Geneva Convention treaty.

Hague Convention of 1899 and 1907
Two conventions were held at The Hague in the Netherlands with an objective to sort out international law for peaceful settlement of international dispute. This convention was important from the view point of laying international law during conflict. Duties and rights of national states, prohibiting bombardment on undefended people, limiting armament etc. were important outcomes of this convention. This convention also led to establishment of Permanent Court of Arbitration. The third conference was scheduled to be held in 1914, but due to outbreak of First World War, third conference could not be held.

League of Nations (1919)
League of Nations is also referred as Child of First World War. When the leaders of Western nations met at the Paris Peace Conference, they decided to form an international organization which can solve international disputes and should not allow repeat of incidents like World War. It was established under the Treaty of Versailles.

The main provision of the covenant of League of Nations was to settle disputes through peaceful methods such as arbitration, negotiation etc., before resorting to disputes. If any member resorted to war, going against the principle of covenant of League of Nations, then the member will be considered as an enemy of whole League of Nations. Permanent court of International justice was established by the League of Nations. Due to various reasons, league was not able to perform its cardinal objective which led to the outbreak of Second World War, therefore new organization, the United Nations came into existence.

Locarno Treaties (1925)
Locarno treaties were result of negotiation between France, Germany, Britain and Italy held in Switzerland in 1925. There were total seven agreements under this treaty. The nations (above mentioned) undertook the obligation not to use force while settling border dispute and peaceful mechanism will be followed. Another objective was to normalize relations with defeated Germany (the Weimar Republic). Later in the year 1936, Germany refused to follow the provisions of the treaty.

Kellogg Briand Pact (1928)
It is also known by the name 'Pact of Paris', the General Treaty for Renunciation of War as an Instrument of National Policy. It was devised with the objective to control outbreak of war. This treaty obliged nations to shun it policy to use war as an instrument for settlement of international disputes.

The United Nations (1945)
The failure of League of Nations led to the Second World War. At the end of Second World War, a new organization came into existence i.e. the United Nations, with the aim to protect world from future war. It was established on 24th October, 1945, when heads of 50 governments met at San Francisco for a conference and drafted UN Charter. At present, this organization is nodal point of international law. It aims at maintaining international peace and security, ensuring friendly relation between nations and achieving international cooperation.

Dimensions of International Law
International law is multi-dimensional in nature, some important dimensions of international law are given below:
Public and Private International Law
International law is divided into two types i.e. Public and Private international law. Jurists have varied opinion on categorization of international law. When international law governs relationship and intercourse between two States, it is known as Public international law. It covers the areas like territorial boundary, diplomatic relations, armed conflict, human rights issues etc. Public international law is implemented according to the provisions of the treaty and agreement. When a part of international law deals with the private citizen of different countries or other related issue, it is referred as private international law.

According to P.E. Corbett:
Private international law is the body of rules for determining question as to selection of appropriate law, in civil cases which present themselves for decision before the Courts of one State or country, but which involve a foreign element, i.e. which affects foreign country or with reference to some foreign system of law.

Major Differences between Private and Public international Law

1. Public international law is more important than private international law.
2. Public international law deals with States and on the other hand, private international deals with individual.
3. Public international law is similar for all the countries, while private international law varies from one country to another.
4. Public international law is formulated by international organizations, based on customs and treaties, while private laws are framed by legislature of respective nation.
5. Implementation of public international law is quite intricate task as compared to the private international law.

Is International Law a True Law or Not
This is the biggest question till date on the nature of international law, whether it should be considered as a law or not. There had been controversy over it, many jurists such as Hall, Lawrence, Frederick Pollock etc. perceive it as a law where as John Austin, Holland, Jeremy Benthem deny the fact.

Jurists who were against It
Most important name in this regard is of John Austin, he believed that international law is not a true law. According to him, International law is not a true law, but a code of rules and conducts of moral force only.

He said that there is no sovereign authority which provides for the enaction of international law, rather it depends on the will of nation to ratify it. He described international law as positive international morality consisting of opinions or sentiments current among nations.

Another jurist Holland also denied international law as a true law. He said that international law is distinct from municipal law as it not supported by the authority of law. According to him, international law is vanishing point of jurisprudence.

He also states that international law could not be kept in category of law because it lacks sanction, which on another hand is integral feature of municipal law. Other prominent jurists who supported this idea were Jeremy Bentham and Jethro Brown.

Jurists Who Supported It
Many jurists supported the fact that international law is law in true sense. Most important name in this regard is Sir Frederick Pollock, according to him, international law satisfy the condition required to be a law. It has been properly formulated by competent political community and recognised by the members on whom it will be implemented.
Hall and Lawrence also supported this view. They said that international law is treated and enforced like law. According to them, international law is based on custom and precedent like other municipal law.

Subjects of International Law
International law consists of different subjects. However, jurists have diverse opinion regarding subject of the international law, as subject in international law is synonymous with the 'under rule jurisdiction or control'.

There are three stories to understand it, which are as follows:
States Alone are Subject of International Law
Professor L Oppenheim and Percy E Corbett are main supporters of this theory. As per them, State and States alone are part of the international law. According to Professor L Oppenheim, since law of nation is primarily a law between States and codified by them, thus, only States should be considered as part of international law. According to Percy E Corbett, States are the only subject of international law and individuals are only incumbents of rights and duties at international law in so far as they are object and not subject.

Only Individuals are Subject of International Law
Professor Kelson is considered as chief profounder of this theory. According to him, In the international law, duties of States are ultimately the duties of the individual. Hence, there is no distinction between international and state law. According to the Nuremberg Tribunal, International law imposes duties and liabilities upon individuals as well as upon states. Therefore, individuals can be punished for the violation of international law.

States, Individuals and Other Non-State Entities are Subject of International Law
As per this view, all States, individuals and other non-State entities are subject of international law. The Permanent Court of International Justice, in Donzing Railway official case stated that, in any treaty, the intention of the parties is to confer on some individuals with certain rights, which the international law will recognise and will enforce them.

Relationship between International Law and Municipal Law
Municipal law is commonly known as State law. There are different perspectives regarding relationship between international law and municipal law. According to some jurists there is intricate relation between them, while others deny any relationship between them.

There are many theories which have discussed relationship between International law and Municipal law, which are as follows:
Dualistic Theory (International law is considered as inferior to domestic law)
The chief propounder and supporter of this theory are Triepel and Anzilotti. They view international law and municipal law different from each other. Both of them hay different sources and scopes. Dualistic believes that international law does not form part of domestic law of State. International law is considered as inferior to domestic law. According to Triepel, the difference between international law and municipal law is in the area of subject, principles, origin, source, substance of law and subject matter.

Monistic Theory (No distinction between international and municipal law)
Monistic theory was contradictory to the dualistic theory, According to this theory, they are flip side of same coin and there is no distinction between international and municipal law. As per monistic supporter, both the laws have same objective such as ensuring peace and security, etc. This theory believes that both the laws are interconnected and interdependent, also individuals are ultimately subject of each other. Followers of this theory stated that international law is superior than the domestic law.

Transformation Theory
It is another perspective, which says that with time international law undergoes transformation into municipal law. Hence, international law acts as a source of municipal law. Through transformation procedure, rules set by international treaties are extended to individual of state through ratification of treaty and enaction of law.

Adoption of Kyoto protocol, convention on child labour by the nations are some of the examples of transformation theory.

Delegation Theory
In reaction to transformation theory, delegation theory came into existence. According to this theory, international law did not directly transformed into municipal law, but it is decided by State on its own when the provisions of a treaty or convention are to be made effective and in which manner. Legislature of State is final body in formulating international law into municipal law.

Specific Adoption Theory
This theory laid down the principle of adoption, which is based on the principle that international law cannot be directly enforced through municipal law. So, execute international law into country, a country has to adopt it. This adoption principle is based on the international conventions such as Hague Convention 1970, Vienna Convention etc., which provided that law enacted by international organization or Convention may be adopt by the nations to include in their municipal law. In the case of Jolly George v. Bank of Cochin 1980, the court held that any agreement does not automatically become part of municipal law, but the positive commitment of state parties inspires their legislative action.

Scope and Content of International Law
Scope:
There is no theory or measures through which we can understand scope of the international law. Generally, whole world is considered as a jurisdiction of international law. For instance, there are currently 193 members of the UN, so protocols, rules, conventions, decisions of the UN will have impact on all 193 nations. All the states whether small or big, developed or developing etc., are equal in the eyes of international law. International law does not only cover states but also regulate international organisations, business, non-profit entities and individuals. According to eminent jurist, state, individual and non-state entities are part of the international law.

Content
International law consists of following contents:
Laws Governing States at the Time of Peace
During peace time, international law includes obligations and rights on nations and international organisations to fulfill its objective of equality of States and respecting their sovereignty. It consists of treaties and customs, whose provisions will be implemented during peace time. It covers the rights of officials and diplomatic representatives of nations and organisations. It ensures that every nation should do things without trespassing into sovereignty of other nation.

Laws Governing at the Time of War
There are specific laws to deal with the contingency situation like war. International law have onus to avoid war, if still it occurs then there are rules and regulations to solve the dispute or stop the war as early as possible. The rule book of international law contain provisions regarding declaration of war, the classification of wars, law and custom of war on land, sea and air, the after effect of war and how to deal with the problem of war prisoners. At global level, various conventions and treaties have been enacted, which prohibited use of cruel tactics such as biological and chemical warfare in the field of war and also prohibited bombardment of civilian areas during Conflict.

Laws Governing at the Time of Neutrality
It is also very important section under international law. According to principle of neutrality, the belligerent state has specific duties towards neutral state and similarly neutral state has some duties toward belligerent states.

Basis of International Law
In universe, everything has some basis, in the same way there are different basis of international law. There are two main theories which tried to explain the basis of international law. These are as follows:
Theories as to the Law of Nature
Grotius, Starke, Vattel, Pufendorf etc., were chief exponents of this theory. This theory laid emphasis on law of nature as a basis of international law. The jurist Grotius had expounded the concept of the law of nature. According to him, natural law was the 'dictate of right reason'. According to followers of this theory, law of nature has been derived from the nature of man. Law of nature is considered as supreme, thus it is binding on others. Jurists argue that international law is a part of the law of the nature.

Municipal law incorporates international law because it is part of law of nature. Some jurists reasoned that law of nature emanates from God or reasons or morals. This theory was hailed by lot of intellectuals, but there were many inbuilt limitations such as how international law can be binding on the nations, etc. Different exponents used different meaning to the law of the nature. This theory is not much realistic in nature.

Positivism
Bynker-Shock is the chief exponent of the positivism. Other supporters of this theory were Starke, Brierly and Anzilotti. It is based on the principle of law positivism, which means fact as contrasted with law which ought to be. Positivists believe that law enacted by competent authority is binding on the subject. According to Starke, international law can in logic be reduced to a system of rules dependent for their validity on the fact that States have consented to them.

According to Brierly, the doctrine of positivism teaches that international law is the sum of rules by which States have consented to be bound and that nothing can be law to which they have not consented to be bound.

According to Italian Jurist Anzilotti:
the binding force of international law is based on a fundamental principle known as Pacta Sunt Servanda.
But the positivist theory fails to explain the binding force of customary rules of international law.

Other Theories Related to its Basis
Beside nature of law and positivism, there are many other theories related with the basis of international law, which are as follows:
Theory of Consent
One of the most important theories regarding basis of international law is the theory of consent. This theory heavily emphasizes that consent of a State is important in the implementation of international law. Consent can be either explicit or implicit. This theory was also supported by the propounder of positivist theory such as Anzilotti, Triepel, Oppenheim etc. States observe rules of international law because they have given their consent for it. Other jurists who criticized this theory were Starke, Brierly, Kelsen, Fenwick etc.

Auto-Limitation Theory                                                        
This theory is quite similar to the theory of consent. Jellinek was main propounder of this theory. Auto-limitation theory says that international law is binding on State because States have restricted their power through the process of auto-limitation. This theory was also supported by positivist. Each state has a free will and its sovereign but by utilizing the process of auto-limitation, it can allow implementation of international law on it. Thus, we can say that international law is not binding on nation but through adoption and ratification, they allow international law in their municipal law.

Theory of Fundamental Rights
This theory is derived from the idea of law of nature. According to this theory, as individual has fundamental rights, similarly State also possesses certain fundamental rights. Fundamental right of States includes sovereignty, equality, self-determination, independence etc. Due to inherent fundamental rights in the State, no institution at global level is over and above the State.

Pacta Sunt Servanda
'Pacta Sunt Servanda' means if state enters into agreement, then it should follow and respect it in good faith. Chief exponent of this theory was Italian jurist, Anzilotti. According to him, 'Pacta Sunt Servanda' is basis of binding force of international law. This principle is based on the idea of actual practice of law.

Sources of International Law
Sources are like foundation which can be referred to as procedure, method or way through which international law is created. These resources provide legal framework to the international law, as virtue of which it is observed by the State.

According to Starke:
The material source of international law may be defined as the actual materials from which international lawyer determine the rules applicable to given situation.

Important sources of international law are as follows:
Treaties and Conventions
Treaties and conventions at global level are most important sources of international law. According to Article 2 of the Vienna Convention on the law of treaties, 1969, A treaty is an agreement whereby two or more States establish or seek to establish relationship between them governed by international law.

Article 38(1) (A) of the International Court of Justice (CJ), uses the term international convention and emphasises upon treaties as a source of contractual obligation, but also acknowledges the possibility of a State expressly accepting the obligation of a treaty.

Treaty and convention are based on the theory of consent and auto-limitation. Protocols are also included under treaty and convention. When a country signs and ratifies treaty and convention, then it becomes obliged to its provision. The provision of treaty can be both binding and voluntary in nature. Geneva, Child Labour Conventions are some of the examples of international treaty and convention.

Treaties and conventions ensure help in creation of rules of law at global level. Treaties can be of two type viz. law making treaty and treaty contract. Former refers to making various rules and regulations, similarly what legislation does for the State. The UN Charter is perfect example of law-making treaty. Later refers to contract between two or more nations.

International Usage and Customs
Many times, term custom and usage are used synonymously. However, they are different as usage is primary stage of a custom. In international relations, when any State shows some attitude and behaviour, which is repeated in certain circumstances, it is referred as usage. When this attitude and behaviour is recognised by the nation, it is referred as custom. These are considered as the oldest and original source of international law as well as of law in general. According to Starke, usage represents the twilight stage of custom, custom begins where usage ends.

Article 38(b) of the Statute of International Court o Justice recognises 'international custom, as evidence of general practice accepted as law', as one of the sources of international law.
During 19th and 20th centuries, most of customary sources of international law have been codified into treaties and conventions, moreover many of them are gradually displaced by the treaty. However, still customary law are playing significant role in the international law.

Charter of the United Nation
The UN Charter is soul of functioning of the world's biggest organisation. All the member states are obliged towards the provision of charter. At present, it is the important source of international law enacted by the UN.

General Principle of Law Recognised by Civilised State
It is also an important source of international law. The general principle of law means those rules or standards, which are repeated over time and are recognised by international community. According to international organisation, some of the general principles of law are good faith, responsibility, prescription, res judicata, estoppel, subrogation, etc.

Some landmark judgments which recognised general principle of law are:
In Chorzow Factory (Indemnity) case, judge applied principle of res judicata and also held that one who violates a rule is liable to make separation.
In Mavrommatis Palestine Concessions case, the court applied the general principle of subrogation.

Judicial Decision
Judicial decisions of International Court of Justice and Arbitral tribunals have also acted as a source of international law. Article 59 of the statute of the International Court of Justice provides that the decision of the court will have no binding force except between parties and in respect of that particular case. However, decision can establish new precedent and international organisation and States can enact law following the interpretation of judgment. In comparison to above listed sources, it is not direct source of international law. It is important to note that sometimes judicial decision by State may also become source of intentional law. It can be through two types, one through established precedent and other through customary law.

Jurist Work as Source
It is generally not considered as important source of international law. However, Article 38(2) (d) of the International Court of Justice states that the 'teaching of the most highly qualified publicist of the various nations is also among the subsidiary means for the determination of the rules of law'.
According to Justice Gray:
Where there is no treaty and no controlling executive or legislative act or judicial decision, resort must be had to the customs and usages of civilised nations, and as evidence of these, to the works of jurists and commentators who by years of labor, research and experience have made themselves peculiarly well-acquainted with the subjects of which they treat. Such works are resorted to by judicial tribunal, not for the speculations of their authors concerning what the law ought to be, but for trustworthy evidence of what the law really is.

International Comity
Principle of comity means, when any nation behaves and shows attitude in particular way and in return other nation also behaves in similar way and show same attitude. Jurists like Professor Oppenheim have supported it and said that principle of comity, helped in development of international law. It even acted as a base of mutual relationship between nation and organisation.

State Paper
State paper includes letter, MOU etc., exchanged between nations. It is the result of diplomatic relations between the States. In a study by some researchers, it was found that state paper helped in solution of disputes and acting as a motivational force to create new law at international level.

Equity and Justice
Equity and justice are the foundations of international law. The purpose for which international laws were enacted was to ensure equity and justice at global level. In the Barcelona Traction case, Sir Gerald Fitzmaurice emphasised the need for a body of rules and principle of equity in the field of international law.

Decision or Determination of the Organ of International Institution
Decision or determination of the organ of international institution also acts as a source of international law. Today UN and its organ, through different means, affect the course of international law. Integral organ of the UN such as the General Assembly have strategic and policy making decisions which are followed by the member nations. Many inter-governmental organisations also known as specialized organs, are also sources of international law.