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International Law
SUNY Buffalo Law School
Mutua, Makau W.

Sources of International Law

Factors influencing the advent of international law:

Increase in Sea Trade
The need to protect international trade
The need to protect diplomacy
The need to protect sea-faring crafts
The pacific settlement of dispute (Peace of Westphalia signed between Protestants and Catholics to end the reign of the Pope as ruler of Europe, following the 30 Year’s War à this launched the modern European state).

International Criminal Court – more limited jurisdiction than the ICJ, as it deals only with crimes against humanity, war crimes, genocide, and acts of aggression.

The ICJ – replaced the Permanent Court of International Justice in 1945.

Countries that are members of the UN are also parties to the ICJ Statute, as that Statute was appended to the UN Charter. Hence, the sources of international law that the ICJ Statute lists are followed by all UN Members.

Jurisdiction of the ICJ:

Contentious Jurisdiction:

Only states can be parties to a suit
Decisions are binding, final and without appeal

Advisory Jurisdiction:

Only UN organs and its specialized agencies can invoke this jurisdiction.
It is a restatement of the law.
Decisions/Opinions are not binding
States/individuals cannot invoke it

Article 38 of the Statute of the International Court of Justice:

The Court shall apply:
1) International Conventions– establishing rules expressly recognized by the contesting states
2) International Custom – as evidence of a general practice accepted as law
3) General Principles – of law recognized by civilized nations
4) Judicial Decisions & Teachings – subject to the provisions of Article 59 [stating that decisions of the Court shall have no binding force except between parties to the case]; will be used as a subsidiary means for the determination of rules of law. It is very difficult to use this alone as a dispositive source of law

Voluntarism: international rules emanate from the free will of states as expressed in conventions or custom (see Lotus).

Positivism: emphasizes the obligatory nature of legal norms and the fixed authoritative character of the formal sources

For something to become customary law, it must be consistent, general, practiced and growing out of a sense of legal obligation (opinio j


Facts: During the Spanish-American War, the US seized two Cuban fishing boats, owned by Spanish citizens. The boat had no knowledge of the war or the blockade and had no weapons. The court held that civilian fishing boats are free from the ravages of war.

Notes: Is International Law a part of U.S. law, so that it can be invoked in domestic U.S. courts?

The U.S. Supreme Court did not apply U.S. law – it applied international law.
There was a convergence between treaties and customs of states, causing the Court to conclude that the custom coalesces into international law and becomes part of U.S. law.

But, the Court only cites to customs of Europeans. Can custom be formulated out of the practices of only 5 countries? A problem with the opinion was that it made no mention of other maritime states, such as China or Japan. But, even if a small amount of states say something is a custom, if other states follow it, in practice it becomes custom.