Private estate on Long Island where Presidents Obasanjo and Biya signed the agreement transferring sovereignty over the Bakassi Peninsula from Nigeria to Cameroon under UN Secretary-General Kofi Annan's mediation, implementing the 2002 ICJ judgment.
Greentree is the former Whitney family estate at Manhasset, New York, now operated as a private foundation hosting confidential diplomatic talks. On 12 June 2006, in the Greentree drawing room, Olusegun Obasanjo and Paul Biya signed what is now known as the Greentree Agreement.
The Agreement implemented the International Court of Justice judgment of 10 October 2002 in the case concerning the Land and Maritime Boundary between Cameroon and Nigeria. The ICJ had awarded the Bakassi Peninsula to Cameroon. The Greentree document set out the modalities of Nigerian withdrawal, the transitional regime for the resident Nigerian population, and the role of UN observers.
Nigerian forces completed the formal handover on 14 August 2006. A residual transitional regime ran until 14 August 2013, after which Cameroonian sovereignty became unconditional.
The Greentree Agreement is the most consequential post-1960 territorial change in Nigerian history. It also stands as one of the few cases in which an African state has implemented an adverse ICJ ruling without resort to force.