Sources of International Law 

The Sources of international law:
Article 38, paragraph 1 of the Statute of the ICJ, declares the Court’s function to decide disputes ‘in accordance with international law’ also details the sources of international law as:
International conventions, establishing rules expressly recognised by the contesting states.
International custom.
Subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations.
The Court has recognised a number of other sources, some are universally recognised.
Other sources of international law include unilateral acts of international law by states and the decisions of certain international organisations,
An important source of obligation in international human rights law is soft law.
The term ‘soft law’ is a misnomer, as law is ‘hard’ but it is also flexible.
It does encompass treaties (which are formal law) but which contain loose obligations or voluntary resolutions.
Treaties:
The law that regulates treaties is neatly encapsulated in the 1969 Vienna Convention on the Law of Treaties.
In many senses, this law highlights some of the issues concerning sources of international law and their relationship.
The Vienna Convention is binding upon those who are party to it, as a treaty, and upon others as customary international law.
The principal human rights treaties:
The main treaties for our purposes are:
The International Covenant on Civil and Political Rights 1966
The International Covenant on Economic, Social and Cultural Rights 1966
The Convention on the Elimination of all Forms of Discrimination against Women 1979
The Convention against Torture, Cruel, Inhuman or Degrading Treatment or Punishment 1984.
The UN Convention on the Rights of the Child 1989 AND
The Hague and Geneva Conventions
Definition of Treaty:
A treaty is defined in the Vienna convention on the Law of Treaties (VCLT) 1969 as ‘an international agreement concluded between states in written form and governed by international law…’ (Article 2(1)(a))
The Vienna Convention is regarded as reflecting customary international law, and the definition of a treaty is accepted as referring to those agreements which are:
In written form (treaties can be unwritten, but in this the VC does not apply)
Between states
Governed by international law
Treaties can either be between two parties or states (bipartite or bilateral) or between number of states or parties (multipartite or multilateral).
The relationship between treaties and customary law:
Treaties and customs have a clear relationship between them as the same obligation can extend to the same state from either source. Thus the source of a treaty can be a treaty or a custom, or sometimes both.
There is a complex relationship between treaties and customary law; the two sources tend to, in practice, overlap. If not, they may leave an intermediate area between them.
The habit of drafting and debating the provisions of a treaty often leads to clarify as to what is the content of the customary rule.
Treaty law will usually supersede the previous contrary customary international law.
It can be said that in an event of inconsistency, whichever is the most recent-be it custom or treaty-prevails between the same parties.
However, more specialised rules tend to prevail, or more general ones in the event of a conflict.
Article 53 of the Vienna Convention on the Law of Treaties does void and terminate an existing treaty if a new peremptory norm of general international law emerges.
A ‘peremptory norm’ is one that is considered superior to other rules of international law.
The formal definition of a peremptory norm exists in Article 64 VCLT, which defines it as: “A norm accepted and recognised by the international community of states as a whole.
Reservations:
A reservation is indicative of the consensual nature of international law.
A reservation is where a state seeks to exclude the application to it of certain provisions of a treaty which it is otherwise willing to accept.
Article 2(1)(d) VCLT: “(a) unilateral statement, 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.”
The traditional approach was that a state could only insert a reservation if all other states to the party consented. This would make meaningful law-making virtually impossible.
The ICJ, in 1951, was requested to provide an Advisory Opinion on the matter of validity of reservations.
In its Advisory Opinion, the court adopted a more flexible and realistic approach,
Article 19 VCLT, states that a party may, when signing, ratifying, accepting, approving or acceding to a treaty, formulate a resolution unless: