(continuing the series on sources of international law)
Treaties are an important source of international law, as well as a critical tool for international relations.
Three Main Types of Treaties
There are three important types or classes of treaties. The first is the general multilateral treaty. This type of treaty is one that is open to all states of the world (or if it’s a regional multilateral treaty, open to all states in the large regional group). The critical role of the multilateral treaty is to lay down rules of behavior (laws) that tend to be of a fundamental and “norm-creating” character. In other words, many of the principles and rules that make up multilateral treaties also form the basis of general rules of law.
Another important class of treaties are those that establish a collaborative mechanism by which states can regulate or manage a particular activity. These treaties tend to lay out a specific purpose or objective and then back it up with legal principles. Collaborative mechanism treaties usually operate through decisions made by their main organs and central governing bodies. They tend to have an institutional and administrative character that allows them to oversee various areas of activity.
The third important class of treaty is the bilateral treaty. These treaties are those made between a small number of states (not necessarily just two, but generally less that four or five). Bilateral treaties often are drafted in contractual terms in which the parties mutually exchange rights and obligations. They are usually detailed and provide for specific conditions that dictate the parties’ rights and duties. Common examples of this type of treaty include treaties of alliance, trade, friendship, etc.
Cross-Over Concepts with Customary International Law
With certain obvious differences (such as treaties based on written agreements by parties), customary international law and treaties intersect in important ways in regards to the formation of international laws.
One such cross-over is the concept of entanglement. This occurs when provisions in treaties also rise to the level of customary international law. When this happens, a state might be bound to a provision of a treaty even when that state is not a party to the treaty. As a member of the international community, states agree (assuming they are not the persistent objectors discussed in Part I) to be bound by customary international.
This can be a tricky concept that is difficult to grasp, but at the core, the essential aspect is that the rule itself is customary international law. Therefore, the codification or inclusion of the rule in a treaty merely serves to emphasize and state that what is already law.
Another important concept is that of instant custom. This occurs when a provision or rule in a treaty is agreed to by a large number of countries, including all specially affected states. When the number in agreement is substantial enough, the provision or principle instantly establishes a rule of customary international law. The need for a large number of states to be in agreement necessarily means that this requires the treaty to be a multilateral treaty.
As with other forms of customary international law, a state may oppose the rule and be a persistent objector. When instant custom is at issue, a persistent objecting state must dissent throughout the formation process. This must be in the form of actual debates and discussion in opposition.