United States v. Maine

Background

A long-running dispute brought by the federal government against coastal States began in 1969 to decide where each State’s coastline lies for setting seaward boundaries and ownership of the seabed. The key question was whether Long Island Sound and Block Island Sound are, in whole or in part, a juridical bay under the Convention on the Territorial Sea and the Contiguous Zone, because a bay’s closing line becomes coastline and affects state jurisdiction. A Special Master found the Sounds together form a juridical bay and that the bay closes on a straight line from Montauk Point (Long Island) to Watch Hill Point (Rhode Island). The United States, New York, and Rhode Island filed exceptions to that Report.

Reasoning

The central issue was whether Long Island can be treated as an extension of the mainland so that Article 7’s bay tests apply. Article 7 requires a well-marked indentation, landlocked waters, an enclosed area at least as large as a semicircle, and a mouth no more than 24 miles. After reviewing the evidence, the Court agreed that Long Island’s shape, proximity to the mainland, the shallowness and inutility of intervening waters, their common geological origin, and patterns of navigation make Long Island realistically part of the mainland. The Court rejected the States’ argument that Block Island should change the closing line, finding Block Island too remote and the waters east of the Montauk–Watch Hill line insufficiently sheltered to be part of the inland bay.

Real world impact

The Court adopted the Special Master’s recommendations, overruled the exceptions, and directed the parties to submit a decree. As a practical result, waters west of the Montauk–Watch Hill closing line are internal State waters (with seaward boundaries measured from that coastline), while waters east are territorial or high seas. The ruling affects state authority over the seabed, pilotage rules, and regulatory powers in those waters.