United States v. Louisiana

Background

The dispute involved the United States, the State of Mississippi, and the State of Alabama over where the coastline should be drawn and which submerged lands belong to the States or the United States. A Special Master concluded that the whole of Mississippi Sound constitutes historic inland waters. The Court overruled the United States' exception to that conclusion on February 26, 1985, and later directed the parties on March 1, 1988 to submit a proposed decree. The parties agreed and submitted a decree, and the Court entered this Supplemental Decree adopting the Master’s recommendation and defining specific coastal baselines and coordinates. Justice Marshall did not participate.

Reasoning

The core question was whether Mississippi Sound should be treated as state inland waters for purposes of a 1960 decree that sets the boundary between state and federal submerged lands. The Court accepted the Special Master’s finding and overruled the United States’ challenge, adopting detailed lines and coordinate points that define Alabama’s coastline and Mississippi’s baselines around islands such as Petit Bois, Horn, and Ship Island. The decree fixes these baselines as of its entry date so they are no longer changing with shifting shorelines, and allocates costs and Special Master compensation between the parties.

Real world impact

This decree determines which waters and submerged lands are controlled by the States rather than the federal government for the Mississippi Sound area. That affects control over coastal resources, management, and any rights tied to the seabed in the defined area. By fixing baselines with precise coordinates the Court makes the boundary stable for enforcement and resource claims, at least as to this decree. The Court also retained jurisdiction for any further orders, so future adjustments or proceedings remain possible.