Introduction to International and Comparative Law
a state other than their own, they may be held accountable by the other state, under the principle
of objective territoriality jurisdiction.
The Making of International Law
Within states, law is made by legislatures, courts, and other agencies of government. However, at
the international level, no formal lawmaking machinery exists.
Under Positivist principles, international law comes into effect only when states consent to it. The
general consent of the international community can be found in state practice, that is, in the
conduct and practices of states in their dealings with each other. Statements or evidence of
general consent can be found in the decisions of the International Court of Justice (ICJ), in
resolutions passed by the General Assembly of the United Nations, in lawmaking multilateral
treaties, and in the conclusions of international conferences. When a provision is repeated over
and over in bilateral treaties, courts and law writers will regard the provision as having the
general consent of the international community.
Sources of International Law
The sources of international law are what courts and other international tribunals rely on to
determine the content of international law. Article 38(1) of the Statute of the ICJ lists the sources
that the court is permitted to use. This listing implies a hierarchy, or order, in which these sources
are to be relied on.
Treaties and Conventions – Treaties are legally binding agreements between two or more states.
Conventions are legally binding agreements between states sponsored by international
organizations. Both are binding upon states because of a shared sense of commitment and
because one state fears that if it does not respect its promises, other states will not respect their
promises. Most of the customary rules that once governed treaties are contained in the Vienna
Convention on the Law of Treaties, which came into force in 1980.
Custom – Some rules have been around for such a long time or are so generally accepted that
they are described as customary law. International customary law is constantly changing.
To show that a customary practice has become customary law, two elements must be established
—one behavioral and one psychological. The first—called usus in Latin—requires consistent and
recurring action (or lack of action if the custom is one of noninvolvement) by states. The second
element in showing that a customary practice has become law is the requirement that states
observing the custom must regard it as binding. This is often referred to by the Latin phrase
opinio juris sive necessitatis.
Even if the international community follows a practice and recognizes it as binding customary
law, under some circumstances the rule will not apply to a particular state. This happens when a
state persistently objects to a practice during its formative stages and thus never becomes a party
to it. This can also happen after a customary rule has become generally accepted, if a state is
allowed by the international community to deviate from the general practice.
General Principles and Jus Cogens – When courts are required to decide international disputes,
they frequently rely on the general principles of law that are common to the legal systems of the
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