In this case, the federal government constructed a dam on the Mississippi River, which backed up the water onto a tributary river, reducing the ability of the tributary to produce hydroelectric power for the plaintiff’s own dam. It sued for a taking. The Court held 7-2 that there was no taking.
But the case stands out as much for the clarity of Justice Jackson’s language than anything else:
It is clear, of course, that a head of water has value, and that the Company has an economic interest in keeping the [tributary] at the lower level. But not all economic interests are “property rights;” only those economic advantages are “rights” which have the law back of them, and only when they are so recognized may courts compel others to forbear from interfering with them or to compensate for their invasion. The law long has recognized that the right of ownership in land may carry with it a legal right to enjoy some benefits from adjacent waters. But that a closed catalogue of abstract and absolute “property rights” in water hovers over a given piece of shore land good against all the world is not, in this day, a permissible assumption. We cannot start the process of decision by calling such a claim as we have here a “property right;” whether it is a property right is really the question to be answered. Such economic uses are rights only when they are legally protected interests.As Zasloff writes, "I’m not sure as clear a statement of legal realism or positivism has ever been made." Many, including environmental historians (and also lawyers), often mistakenly attribute great importance to something being called a property right, but as Jackson explains, saying that someone has a "property right" is properly the end of a legal analysis, not its premise.