The concept was developed in the process of settling disputes in which the borders of adjacent nations were located on a contiguous continental shelf: An equidistance line is one for which every point on the line is equidistant from the nearest points on the baselines being used.
The equidistance principle is a methodology that has been endorsed by the United Nations Convention on the Law of the Sea but predates that treaty and has been used by the Supreme Court of the United States, states, and nations to establish boundaries equitably.
[1]The equidistance principle represents one aspect of customary international law, but its importance is evaluated in light of other factors[2] such as history: "Historic rights" or titles of some or another kind will acquire enhanced, rather than diminished, importance as a result of the narrowing of the 'physical' rather than the 'legal' sources of right.
Germany claimed that due to special circumstances they owned that land so the three countries fought through the United Nations.
In the absence of agreement, and unless another boundary line is justified by special circumstances, the boundary is the median line, every point of which is equidistant from the nearest points of the baselines from which the breadth of the territorial sea of each State is measured.