The U.S. Supreme Court case Ohio v. Kentucky in 1972 revolved around a dispute over the boundary line between the two states along the Ohio River. The controversy arose when Kentucky claimed that it owned all of Greenup County, which was on both sides of the river, while Ohio argued that its territory extended to low-water mark on the northern side of this river based on an 1803 law and historical practice. The court ruled in favor of Kentucky by reaffirming a previous decision from Indiana v. Kentucky (1890), stating that when Virginia ceded its land claims to form new states including Kentucky and Ohio, it did not intend for these new territories' boundaries to be affected by changes in water levels or channels over time - thus making them "fixed" rather than "floating". Therefore, despite any subsequent alterations due to natural causes or human intervention such as dam construction causing fluctuation in water level, original state lines should remain intact.

In the dissenting opinion for Ohio v. Kentucky, 1972, Justice William O. Douglas argued that the majority's decision to uphold a lower court ruling on boundary disputes between states was flawed and inconsistent with previous Supreme Court decisions. He contended that the Court should have considered historical evidence of state boundaries rather than relying solely on an earlier compact between Ohio and Kentucky which he believed was ambiguous in its language about where exactly their shared border lies along the Ohio River. Furthermore, Douglas criticized his colleagues' reliance on acquiescence as a basis for determining borders when there were clear indications of dispute over many years from both sides involved in this case.