New Hampshire v. Maine
United States Supreme Court
532 U.S. 742 (2001)
A 1740 royal decree fixed the boundary between New Hampshire (plaintiff) and Maine (defendant) as running "up the Middle of the [Piscataqua] River." In prior 1970s litigation, after extensive historical inquiry, New Hampshire entered a 1977 consent decree agreeing the phrase meant the middle of the river's main navigational channel. In 2000, New Hampshire sued again, this time arguing "Middle of the River" referred only to a particular branch and that the boundary actually ran along the Maine shore, giving New Hampshire ownership of the entire river in that stretch. Maine moved to dismiss, arguing New Hampshire was barred by claim and issue preclusion and by judicial estoppel from reversing its earlier position.
Whether a state may be judicially estopped from asserting a boundary interpretation that is clearly inconsistent with the position it successfully took in an earlier consent decree involving the same boundary.