Foster v. Neilson, 27 U.S. 253 (1829) was a decision by the United States Supreme Court that held certain treaties ratified by the United States, even if otherwise valid and in force, cannot be given effect domestically without a specific act of Congress.[1] [2] The ruling articulated a more restrictive interpretation of the Supremacy Clause of the U.S. Constitution, which automatically grants treaties the force of domestic federal law.[3]
The Foster decision was the first to formulate the concept of "self-execution", which distinguishes between treaties that are "self-executing" (meaning domestic courts can enforce them directly upon their ratification) and those that are "non-self-executing" (which are not directly enforceable in U.S. courts unless Congress passes specific implementing legislation). It was also the first time the Court applied the "intent-based doctrine of self-execution", which examines the text of a treaty, as well as its related documents and negotiations, to determine whether the treaty makers intended it to be self-executing.[4]
The Court's opinion, authored by Chief Justice John Marshall, recognized that the U.S. Constitution, through the Supremacy Clause, "declares a treaty to be the law of the land" and "consequently to be regarded in courts of justice as equivalent to an act of the legislature." However, Justice Marshall immediately adds a qualifying statement that a treaty is only the equivalent of a legislative act when the treaty "operates of itself without the aid of any legislative provision"' when the terms of the treaty "import a contract" or suggest that some future legislative act is necessary, "the treaty addresses itself to the political, not the judicial department; and the legislature must execute the contract before it can become a rule for the Court."[5]
Using this test, the Foster Court held that the treaty provision at issue—which stated that certain land grants from the King of Spain "shall be ratified and confirmed"—was non-self-executing because it suggested that Congress would ratify the land grants through a future legislative act.[6]