Case Concerning the Territorial Dispute (Libya/Chad)
International Court of Justice
1994 I.C.J. 6 (February 3)
Chad (defendant) and Libya (plaintiff) disputed ownership of the economically and militarily worthless but symbolically significant Aouzou Strip along their shared border; Chad relied on a 1955 treaty between Libya and France establishing colonial-era boundaries, while Libya argued the treaty was invalid due to coercion and didn't actually address the border, later militarily occupying and invading portions of Chad including the Strip. After years of failed negotiations and UN involvement, the two nations agreed to submit the dispute to the ICJ.
Whether a prior treaty between two nations that establishes their shared border governs a later territorial dispute over that boundary's location.