Foster (plaintiff) brought suit in federal district court against Neilson (defendant) to recover a tract of land in Louisiana. Foster claimed he owned the land based on a grant from the Spanish governor. Neilson, the possessor of the land, claimed that the grant made by the Spanish governor to Foster was invalid because it was made after the territory on which the land was situated had already been transferred to France and the United States. The district court accepted Neilson’s argument and held the grant to Foster to be void. Foster appealed and the United States Supreme Court considered the case on a writ of error. The executive and legislative branches of the United States Government previously made pronouncements that the territory in question had been a part of the United States at the time of the Spanish governor’s grant to Foster. Thus, the Supreme Court held it was required to conform its own decision to the decisions made by its fellow branches. However, Foster also based his argument on Article 8 of the Treaty of Amity, Settlements and Limits, which was concluded between the United States and Spain in 1819. This treaty provided that “all the grants of land made before the 24th of January 1818” by the King of Spain or his authorities, in the territories ceded by Spain to the United States, would be ratified and confirmed to the people in possession of the lands, to the same extent as if those possessors received a direct grant of land from the King of Spain himself. Foster argued that the tract of land in Louisiana was among the territory ceded by Spain to the United States, and thus that his possession of the land was ratified or confirmed by the 1819 treaty between Spain and the United States. The Supreme Court considered the issue of whether the words of the 1819 treaty themselves ratified and confirmed the grant of land to the possessors, or whether they merely stated the intent of the United States Government to pass additional legislation ratifying and confirming the land to the possessors.