In the case of State of New Hampshire v. State of Maine in 2000, the U.S Supreme Court was asked to resolve a boundary dispute between the two states regarding their shared maritime border. The controversy centered on whether an agreement made by both states in 1977 accurately represented the historical intent and understanding of where this border should be located. New Hampshire argued that it had been misled during negotiations for this agreement due to incorrect information provided by Maine's expert witness, thus making it invalid. However, after reviewing evidence from both sides including maps and documents dating back several centuries as well as considering international law principles for defining borders, the court ruled unanimously against New Hampshire. It found no reason to overturn or revise its previous approval (in 1977) of what is known as "Middle-of-the-River" line which places most Piscataqua River within Maine’s jurisdiction.

The dissenting opinion in the case of State of New Hampshire v. State of Maine, 2000, argued that the Court should not have dismissed New Hampshire's motion to reopen a 1977 decree determining the maritime boundary between these two states. The dissenters believed that new evidence presented by New Hampshire could potentially prove significant enough to warrant reconsideration of the original judgment. They contended that while there is indeed a high bar for reopening judgments due to concerns about finality and stability, this does not mean such actions are never justified or permissible. In their view, if compelling new evidence emerges which was previously unavailable and could significantly impact an earlier decision - as they believe was true in this case - then it may be appropriate to revisit past rulings rather than rigidly adhering to them regardless of potential errors or oversights.