## Facts

- The boundary between New Hampshire and Maine traces to a 1740 royal decree setting the line “up the middle” of the Piscataqua River.
- In 1970s litigation between the States over a seaward (lateral) marine boundary and related fishing interests, the parties jointly urged that “Middle of the River” meant the middle of the Piscataqua River’s main navigable channel.
- The Supreme Court rejected a Special Master’s geographic-center view and entered a 1977 consent decree adopting the parties’ interpretation: “Middle of the River” means the middle of the main channel of navigation of the Piscataqua River.
- The 1977 decree fixed the lateral marine boundary seaward from Portsmouth Harbor but did not expressly fix the inland river boundary.
- In 2000, New Hampshire filed a new original action asserting the inland boundary runs along the Maine shore, such that New Hampshire owns the entire Piscataqua River and all of Portsmouth Harbor.
- Maine moved to dismiss, arguing New Hampshire’s new position was barred by judicial estoppel (among other doctrines) because it contradicted New Hampshire’s successful position in the earlier litigation.

## Issues

1. Whether judicial estoppel bars New Hampshire from asserting that the Piscataqua River boundary runs along the Maine shore after New Hampshire earlier prevailed on a position that “Middle of the River” means the middle of the main navigable channel.

## Decision

- The Supreme Court unanimously granted Maine’s motion to dismiss.
- The Court held that judicial estoppel bars New Hampshire from asserting that the Piscataqua River boundary runs along the Maine shore.
- The Court did not resolve the historical merits of the inland boundary interpretation because estoppel was dispositive.

## Legal Principles

- Judicial estoppel protects the integrity of the judicial process by preventing a party from taking inconsistent positions to suit changed interests.
- The Court declined to impose an inflexible test, but identified recurring factors:
  - A party’s later position is clearly inconsistent with its earlier position.
  - The party previously succeeded in persuading a court to accept the earlier position.
  - Allowing the inconsistent position would create an unfair advantage or impose an unfair detriment on the opposing party.
- Judicial estoppel is distinct from claim and issue preclusion and may apply even when traditional preclusion analysis is uncertain.

## Conclusion

Because New Hampshire previously obtained a Supreme Court decree adopting its interpretation that “Middle of the River” refers to the middle of the main navigable channel, it could not later claim the same phrase places the boundary along Maine’s shore; the complaint was dismissed under judicial estoppel.


New Hampshire v. Maine, 532 U.S. 742 (2001)