On July 15, the Pelindaba Treaty, which established Africa as a nuclear-weapon-free zone, finally entered into force. The treaty is the latest regional agreement to ban nuclear weapons in its area of application. The other five are the 1959 Antarctic Treaty, the 1967 Treaty of Tlatelolco (for Latin America and the Caribbean), the 1985 Treaty of Rarotonga (for the South Pacific), the 1995 Treaty of Bangkok (for Southeast Asia), and the 2006 Treaty of Semipalatinsk (for Central Asia).

The Pelindaba Treaty--named for the former South African nuclear weapons facility near Pretoria--requires each party "to prohibit in its territory the stationing of any nuclear explosive devices," while allowing parties to authorize visits or transits by foreign nuclear-armed ships or aircraft. It also prohibits nuclear weapon tests and radioactive waste dumping. Two supplementary protocols to the treaty provide for non-African nuclear powers to agree that they won't "contribute to any act which constitutes a violation of this treaty or protocol." The United States co-signed the treaty's protocols under the Clinton administration in 1996, but after a heated political debate, Washington didn't submit them to the Senate for ratification. China, France, and Britain haveclaim that the treaty made the "entire Southern hemisphere free of nuclear weapons." ratified them, however, ostensibly supporting the International Atomic Energy Agency's enthusiastic (if slightly exaggerated)

Underneath this international support for an African nuclear-weapon-free zone, however, is a low-profile but high-stakes dispute over the status of the Chagos Archipelago, which includes Diego Garcia. This coral atoll in the British Indian Ocean Territory happens to be the site of one of the most valuable (and secretive) U.S. military bases overseas. Both Britain and Mauritius claim sovereignty over the archipelago.

According to the map appended to the Pelindaba Treaty, the nuclear-weapon-free zone explicitly covers the "Chagos Archipelago--Diego Garcia," albeit with a footnote (inserted at the British government's request) stating that the territory "appears without prejudice to the question of sovereignty." (To read more about the negotiations that led to the ominous Diego Garcia footnote, see the U.N. Institute for Disarmament Research publication, "The Treaty of Pelindaba on the African Nuclear-Weapon-Free-Zone.") Although all of the participating African countries agreed that the Chagos Islands should be included in the treaty parameters, the British Foreign and Commonwealth Office (FCO) did not, stating that it had no doubt as to its sovereignty over the British Indian Ocean Territory, and upon signing the protocols noted that it did "not accept the inclusion of [the Chagos Islands] within the African nuclear-weapon-free zone" without consent of the British government.

While Russia refused to sign the Pelindaba protocols because of the ambiguity created by that unilateral statement, Britain's interpretation of the footnote was supported by the United States and France, with a representative of the U.S. Arms Control and Disarmament Agency explaining that it was adequate to "protect U.S. interests because any resolution of the [sovereignty] issue will occur outside the framework of the treaty."

But what are the U.S. interests and what exactly does this sovereignty debate have to do with Africa's nuclear-weapon-free zone? In the last 40 or so years, thanks to a series of U.S.-British bilateral agreements (some of them secret), the expulsion of the atoll's indigenous population between 1967 and 1973, and a $2.5 billion U.S. military construction program, Diego Garcia has developed into a robust naval support facility, satellite tracking station, and bomber forward-operating location. It played a central role in all offensive combat missions against Iraq and Afghanistan from 1991 to 2006 and was used as a staging area for 20 B-52 bombers prominently deployed as a "calculated-ambiguous" tactical nuclear deterrent against any possible chemical or biological weapons used by Iraq against U.S. forces. The Diego Garcia internal lagoon--a gigantic natural harbor, measuring 48 square miles and dredged to a depth of 40 feet as a turning basin for aircraft carriers and nuclear submarines--is currently being upgraded to accommodate the U.S. Navy's new nuclear-powered, guided missile attack submarines. Considering the base's strategic location, current U.S. needs in the Middle East and Central Asia, and what is known about past uses of the base, it would be irresponsible to rule out the potential for nuclear weapons at Diego Garcia.

That the United States found the Pelindaba footnote to be adequate protection against the "bite" of the treaty protocols may have been overly confident. Now that the treaty has entered into force, Mauritius and Britain are legally bound by its provisions--though the British FCO would vehemently disagree, citing the footnote as disclaimer. A recent editorial in the Mauritius Times called on the government to broaden its ongoing bilateral negotiations (which will resume in London in October) with the FCO on the Chagos Archipelago to include U.S. authorities (pointedly referring to President Barack Obama's Prague speech), with a view toward making Diego Garcia nuclear-weapon-free. Until that time, in the eyes of Mauritius and the other African signatories to the Pelindaba Treaty, Mauritius will not be able to meet its treaty obligations.

One key to these talks may be the precedent of the 1959 Antarctic Treaty, which also contains a disclaimer for sovereignty issues. Thus far, nobody has interpreted this disclaimer as excluding the British Antarctic Territory from the geographic scope of that treaty. As such, Britain may be forced to confront some inconvenient internal contradictions lurking in the wake of the Pelindaba Treaty. To the embarrassment of the FCO, the Diego Garcia base also has been confirmed by the CIA as a destination or transit point for several "extraordinary rendition flights" for suspected terrorists--branding the island as yet another "legal black hole" à la Guantánamo Bay, where neither the British Human Rights Act nor Britain's ratifications of the Geneva Conventions, the U.N. Human Rights Covenants, or the U.N. Convention against Torture apply.

The Pelindaba Treaty should mark the beginning of a momentous new era in Africa, including regional cooperation for the peaceful uses of nuclear science and technology through a new African Commission on Nuclear Energy. But there is the possibility that the Diego Garcia footnote could stand in the way of progress. If Britain, the United States, and Mauritius cannot resolve this debate, then the entry into force of the Pelindaba Treaty hasn't truly made Africa free from nuclear weapons after all.

Bulletin of Atomic Scientists