structural:expansion, information:highlighting
Nigeria

Biya, Abidjo's successor as president, filed suit at the International Court of Justice on 29 March 1994. Cameroon's claim to Bakassi was largely based on the Anglo-German agreement of 1913 and the 1975 Maroua Declaration. Nigeria, on the other hand, argued that the peninsula had been the territory of the chiefs of Old Calabar, who had transferred their title to Nigeria upon its independence. As support for this argument it pointed to the Nigerian collection of taxes in the region, the widespread use of Nigerian passports by its residents, and other signs that the Nigerian state had been intimately involved in the governance of the peninsula. On 10 October 2002, after more than eight years of hearings and deliberations, the court ruled in favour of Cameroon, instructing Nigeria to withdraw immediately from the region.

Although Nigeria initially protested the decision, and although it caused significant unrest in Bakassi, Olusegun Obasanjo 's regime largely cooperated with the ruling. In June 2006, at the Greentree estate in Long Island, New York, the countries signed the Greentree Agreement, which required Nigeria to withdraw its troops from Bakassi by 4 August 2008, and also required Cameroon to protect the rights of the Nigerian citizens who lived in Bakassi. The transfer of the territory to Cameroon proceeded peacefully under the agreement. The Cameroonian government now presents the dispute as a "misunderstanding", and its resolution as "a model of peaceful conflict resolution in Africa."

At the request of Biya and Obasanjo, UN Secretary-General Kofi Annan established the Cameroon–Nigeria Mixed Commission to negotiate a smooth implementation of the International Court of Justice's 2002 ruling. The commission's responsibilities included demarcating the entirety of the Cameroon–Nigeria border, facilitating cross-border cooperation and troop withdrawals from Bakassi, and protecting the rights of locals. The commission was chaired by Mohamed Ibn Chambas and had met 38 times by 2015. As of July 2019, 2,001 kilometres of boundary (out of an estimated 2,100 kilometres) had been surveyed and agreed to by both countries, including the border at Bakassi. In May 2007 in Abuja, the commission finalised the maritime boundary, but in 2015, the Cameroonian government reported that "a few tens of kilometres remain a stumbling block" in finalising the land boundary.