International Judicial Monitor
Published by the International Judicial Academy, Washington, D.C., with assistance from the
American Society of International Law

Spring 2012 Issue

Historic Moments in International Law


Origin of Definition of “Necessity” in the International Law of Self Defense – the Caroline Affair

Historic MomentsBy: James G. Apple, Editor-in-Chief, International Judicial Monitor and President, International Judicial Academy

When the United States under President George W. Bush was considering the invasion of Iraq before and during the month of March, 2003, proponents of such action argued that such action was justified under the international law of self-defense, in this case, anticipatory self defense. Iraq, the argument went, was planning an attack on the United States and its allies, possibly with the use of nuclear or biological weapons (weapons of mass destruction, or WMDs). Thus the U.S was justified in pre-empting such action by launching an attack against Iraq with U.S. forces. The debate over this issue began with a quotation from history – specifically the words of a U.S. Secretary of State in the middle of the 19th Century that were written in connection with an incident that almost provoked a third war with Great Britain. That incident is known as the Caroline Affair.

In December, 1837, a  group of Canadian insurrectionists hoping to induce Canada to break away from Great Britain, in the manner of the United States in the previous century, and establish a Canadian republic, were active on the Canadian side of the Niagara River – in Upper Canada, in what is now known as the province of Ontario. American supporters of the insurrectionists were ferrying arms across the Niagara River using the U.S. steamer Caroline as the transfer ship.

On December 29 of that year, a British Royal Navy force crossed the river, seized the Caroline with a number of its crew aboard, towed her out into the current, fired her and cast her adrift over Niagara Falls. Two Americans, or at least one, were killed in the engagement. The Caroline grounded above the Falls, and later broke up and was swept over it.

American citizens were outraged at the British action. U.S. President Martin Van Buren protested to the British government to no avail. In May of 1838 a force of mostly Canadian rebels led by an American adventurer retaliated, crossing the river, and capturing the British steamer, Sir Robert Peel while it was in U.S. waters. They looted and burned it.

In the years following these incidents, and after a new administration had come into national office, there was an exchange of notes and letters between the new U.S. Secretary of State, Daniel Webster, and the British Special Minister, Lord Ashburton. In a letter to Ashburton dated July 27, 1842, Webster set forth the requirement of  “necessity” in the international law (law of nations) of self defense:

-instant, overwhelming, leaving no choice of means and no moment for deliberation. It will be for it to show, also, that the local authorities of Canada, even supposing the necessity of the moment authorized them to enter the territories of the United States at all – did nothing unreasonable or excessive, since the act justified by the necessity of self defense, must be limited by that necessity, and kept clearly within it.

This characterization of self defense has been used since the time of that letter to analyze whether certain actions or conduct are justified as self defense measures, particularly so-called anticipatory self defense. Webster’s definition was most recently used, as indicated earlier, when during the administration of George W. Bush questions arose about the President’s plans for a “preventive war” against Iraq.

It should be noted, in conclusion, that although the parties (the U.S. and Great Britain) never agreed on whether the British attack on the Caroline was justified, as indicated by the letters and notes that went back and forth between Webster and Ashburton. The parties did not go to war over the dispute, and the controversy was eventually resolved during the negotiations that led up to the signing of the Webster-Ashburton Treaty of 1842 (which dealt mostly with the resolution of various boundary disputes between the United States and Canada).

One contemporary commentator has noted the importance of the Caroline Affair in the history of international law:

With regards to the right to use force in international law, the affair of the Caroline case has once again confirmed the right of self defense and more importantly, has established clear criterion for its invocation and that of anticipatory self defense.

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© 2012 – The International Judicial Academy
with assistance from the American Society of International Law.

Editor: James G. Apple.
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