Treaties regulate state behavior in times of peace and in times of war.

Treaties appear under many names. They are called charter, agreement, protocol, memorandum, pact, exchange of notes, or more than 25 other titles. Regardless of the formal name, if an agreement creates binding rights and obligations between states under international law, it is, in fact, a treaty.

When states take deliberate actions to regulate specific activities and conclude agreements, they create treaties.

Today, treaties are the principal source of rights and obligations in international law. They are generally in writing, and international legal jurists call the sum of these treaties, “lex scripta,” or, “written law.”

At the beginning of this century, we saw the first efforts to write treaties which many states may sign. These are “multilateral” (many sides) treaties. These first attempts to come up with codified, universal international law include the Hague Conventions of 1899 and 1907. These treaties dealt with the laws of war and humanitarian law during war.

We can find the roots of the UN in one of these efforts to codify universal law regarding state behavior. The first such attempt to outlaw “aggression” in all of world politics was the 1919 Treaty of Versailles. Besides formally ending World War I, it led to the establishment of the League of Nations.

States create all international intergovernmental organizations through treaty agreements between them. The UN Charter created the UN, which the founding member states of the UN signed in 1945. States also create the UN’s specialized agencies (e.g. UNESCO) and regional organizations (like observer programs and peacekeeping operations such as UNPROFOR and the UN Military Observer Group supervising the cease fire line in Kashmir) by treaties.

At the most general level, the statement of purpose of the UN Charter binds the signatories to the UN Charter. According to the UN Charter, one of the purposes of the UN is “… to establish conditions under which justice and respect for the obligations arising from treaties and other sources of international law can be maintained.” This quote illustrates the close connection between the United Nations and the development of international law. Also, the UN Charter specifically gives the UN General Assembly the responsibility of promoting and encouraging the progressive development of international law and its codification. UN organizations and conferences have codified vast bodies of customary international law in the form of treaties, and since the end of WWII, the General Assembly has played an important role in this codification.

These codifications include the 1961 Vienna Convention on Diplomatic Relations (which explicitly stated that diplomats are immune from prosecution) and the 1969 Vienna Convention on the Law of Treaties. It has played an important role in the development of international law as well, in addition to codifying customary international law.

Since the founding of the UN, UN member states, organizations, and conferences have registered more than 30,000 treaties with the organization.

Most treaties are bilateral (two sides) meaning between two states. Plurilateral treaties are treaties between a few states. The "law of treaties" is a separate and very specific body of law which covers treaties. It regulates the making of treaties, their interpretation, modification, validity and termination. In 1980, the 1969 Vienna Convention on the Law of Treaties came into force. The states parties negotiated and signed it in 1969, but only came into force in 1980 because at least two-thirds of the signatories had to ratify it. Over 60 states have ratified it. It sets forth provisions for the regulation of treaties between two or more states.

The Vienna Convention on the Law of Treaties accepted a key principle: pacta sunt servanda, which holds that treaties are always valid and enforced. This principle holds that a state government which claims that a treaty obligation is invalid in some particular situation has to prove that it is so; the burden of proof is on it.

Formation of Treaties The basic steps in the treaty-making process include negotiation, signature, ratification, and entry into force. Article 7 section 2 of the Vienna Convention on the Law of Treaties provides that heads of state and heads of government have the power to negotiate treaties by virtue of their functions. A state may also designate a person or persons to represent it in a document called “full powers.” Since negotiations are often long and arduous, states usually designate persons other than heads of state to negotiate.

The International Law Commission It is a body of 35 individuals, sitting as individuals and not as country representatives. Its task: the progressive development and codification of international law.

Progressive development means the preparation of draft conventions on subjects which have not yet been regulated by international law or on subjects which the law has not yet been sufficiently developed by the practice of states.

Codification refers to the more precise formulation or systemization of rules of international law in fields where there has already been extensive state practice, precedent and doctrine. Drawing a clear line between codification on the one hand and progressive development on the other is difficult; they go hand in hand. Sometimes, non-governmental organizations (NGOs) play a key role in drafting multilateral treaties. The existence of the United Nations and its agencies helps them play this role. For example, the Coalition Against Trafficking in Women (an NGO) has drafted and circulated a proposed Convention Against Sexual Exploitation. This NGO has consultative status to the United Nations Economic and Social Council (ECOSOC). In the case of the proposed International Criminal Court, the "World Federalist Association," for example, significantly influenced the draft treaty content and the travaux preparatories.

Concluding of Treaties The process for concluding a treaty may differ depending on its subject matter and whether the treaty is bilateral or multilateral. Parties to international agreements conclude most of their treaty negotiations through either:

1) through signature alone or
2) through a two step procedure where signature is followed by ratification or approval.

We call a state that signs a treaty a signatory state. If the treaty requires ratification, the signatory state becomes a party only if it ratifies the treaty and deposits its instrument or otherwise complies with the terms of the specific treaty. Each state is free to decide whether or not to ratify a treaty. In practice, states conclude about one fourth of all their international agreements through a simple exchange of the legal instruments to which the negotiators have agreed.

For issues of major importance, the terms for the traditional and most solemn form of a nation’s consent to treaty obligations are ratification, accession or adherence. Ratification in international law has a very specific meaning: it is a formal act, the acknowledgment by a state, that the state is accepting the terms of the treaty. The state representatives publicly confirm that their state accepts the provisions of the treaty, and the state formally consents to its constraint by them. A head of state may have to obtain ratification, for example, from his or her own legislature, or through some other domestic political procedure to prove the consent of the people. Only a small percentage of treaties require such a procedure. Sometimes, the constitutions of countries list the types of treaties which require ratification:

the constitutions of France, Belgium and the Netherlands specify the kind of treaties which require ratification. Under the Vienna Convention on the Law of Treaties, article 18, section a, after signing the treaty, the state is under an obligation to refrain from any action that would defeat the object and purpose of the treaty.

Entry into Force The final phase of treaty-making is entry into force. Usually the treaty establishes itself when its provisions take effect. In most cases, this occurs immediately or within a few months after consent is given by the contracting states. Some multilateral treaties require that a certain number of states consent to its provisions before the treaty becomes binding.

Reservations In some cases, a state may become a party to a treaty while opting out from certain provisions. A state may modify the effect of provisions of a treaty to itself by entering a written reservation. A reservation is “ … a unilateral statement, however phrased or named, made by a State, when signing, ratifying, accepting, approving or acceding to a treaty, whereby it purports to exclude or to modify the legal effect of certain provisions of the treaty in their application to that State.” (1969 Vienna Convention on the Law of Treaties, May 22, 1969, art. 2) The Vienna Convention permits reservations unless the treaty itself prohibits them, or they are incompatible with the object and purpose of the treaty. The other states party to the treaty have the option of accepting or objecting to the reservation.

Interpretation A treaty requires interpretation if, after it enters into force, questions arise as to the meaning of its terms. Ø Article 31 of the Vienna Convention on the Law of Treaties formulates the so called “golden rule” of treaty interpretation. The “golden rule” of treaty interpretation is the following: it requires that a treaty be interpreted in good faith, that ordinary meaning be given to its terms, and that the states parties read those terms in their context and in the light of the object and purpose of the treaty.

The context in which the states parties should interpret the particular terms of a treaty consists, first, of the entire text of the treaty with its preambles and annexes. Interpretation must take into account subsequent agreements and subsequent practice along with the rules of general international law together with the context. Interpretation may also consider secondary means. The preparatory works, travaux preparatoires, and the circumstances surrounding the conclusion of the treaty are only secondary means of treaty interpretation. They may be referred to in order to confirm the meaning that was already established according to the textual analysis, or when such an analysis leaves the terms still ambiguous or leads to a result that is clearly unreasonable or absurd.

Invalidity of Treaties The Vienna Convention sets forth the only grounds for invalidity, termination and suspension of a treaty. Invalidity has the most serious and far-reaching consequences and eradicates to the extent possible all legal effects of the treaty.

Four categories of grounds exist for determining whether or not a treaty is invalid:
1) non-compliance with a nation’s internal law
2) error, corruption, or fraud
3) duress, coercion, or threat or use of force.
4) violation of international law.

Category #3, duress, comprises cases in which the consent to be bound by the treaty was procured by a threat or the use of force either against the representative of a state or against the state itself. Article 52 of the Vienna Convention declares that “(a) treaty is void if its conclusion has been procured by the threat or use of force in violation of the principles of international law embodied in the Charter of the United Nations.” A treaty is null and void also if it violates a peremptory norm of general international law.

Article 53 of the Vienna Convention defines a peremptory norm of general international law as a norm which the international community of states as a whole accepts and recognizes and which permits no derogation. "Opinio juris" makes this determination. These international legal theorists very much value jus cogens. The legal consequences of finding a treaty invalid differ according to the grounds. Treaties which are the result of coercion, as well as those treaties in conflict with a peremptory norm of international law are absolutely and retroactively invalid.

Termination of Treaties The Vienna Convention provides that a treaty may be terminated for three reasons:
1) according to its own provisions,
2) by consent of the parties to the treaty, or
3) under the rules of general international law. For treaties not containing a specific provision for denunciation, the prevailing opinion is that states parties may denounce agreements establishing international organizations or dealing with commerce.

States parties may not, however, denounce treaties of peace, treaties establishing international borders, and treaties codifying international customary law. Termination of a treaty may occur under general international law by:
1) the consent of the parties;
2) material breach of one of the parties;
3) supervening impossibility of performance;
4) or substantial change in circumstances. A treaty may always be terminated with the consent of the parties.

So, for example, East Germany was absorbed into West Germany with the consent of East Germany after democratic elections in East Germany, despite the fact that East Germany was a member of the UN. With regard to the Middle East, North and South Yemen merged early in this decade to form one country, despite the fact that they were both signatories of the UN Charter. Only material breach of a treaty may cause treaty termination, or suspension of its operation.

A breach under the Vienna Convention is either a total repudiation of the treaty or the violation of a provision essential to the object and purpose of the treaty. In other words, the parties to a treaty must observe this treaty if it relates to the protection of the human person in a treaty of a humanitarian character even though one of the parties may have breached its obligations under the treaty.

The Vienna Convention allows a party to terminate or to make a claim that the treaty termination is legal on the grounds of fundamental change of circumstances, that is, the doctrine of rebus sic stantibus. However, the Vienna Convention imposes strict limitations on the particular ground. The change must be fundamental and unforeseen. It also must have radically changed the obligation which the parties must perform. However, the party may not rely on that ground to put an end to its obligations under a treaty establishing international boundaries. Nor, can a party rely on that ground when it is responsible for the change in violation of its treaty obligations.