The U.S. Supreme Court case Ohio v. Kentucky in 1979 involved a dispute over the boundary line between the states of Ohio and Kentucky along the Ohio River. The controversy arose when Kentucky claimed that its border extended to the low-water mark on the northern side of the river, while Ohio argued that it was at mid-river point according to an 1792 act by Virginia (which originally included what is now known as Kentucky). The court ruled in favor of Kentucky, stating that historical practice and understanding had established this boundary since Virginia's original cession of territory for creation of new states under Articles of Confederation. Therefore, despite no explicit mention in Congress' acceptance acts or state constitutions about exact boundaries, they were implicitly accepted through long-standing practice and mutual recognition by both states.

In the dissenting opinion for Ohio v. Kentucky, Justice William Rehnquist disagreed with the majority's decision to uphold a 1792 decree that established the boundary between Ohio and Kentucky along the low-water mark on the northern side of the Ohio River. He argued that this ruling was based on an incorrect interpretation of historical documents and treaties, which he believed indicated that both states had originally intended for their border to be at mid-river. Furthermore, he contended that by adhering so strictly to a centuries-old decree without considering subsequent changes in circumstances or attitudes towards state boundaries, such as advancements in survey technology or shifts in public policy preferences, could potentially lead to unjust outcomes. Therefore, he felt it would have been more appropriate for them to adopt a flexible approach when interpreting these old decrees rather than treating them as immutable laws.