The U.S. Supreme Court ruled Jan. 20 in favor of two North Carolina entities seeking to intervene in the case between South Carolina and North Carolina over water rights in the Catawba River Basin.

In an opinion written by Justice Samuel Alito, the court ruled in a 5-4 decision that both Duke Power Company and the Catwaba River Water Supply Project — a joint program between Union County in North Carolina and Lancaster County in South Carolina — met the standard of intervention. Chief Justice John Roberts wrote the dissenting opinion.

S.C. Attorney General Henry McMaster is representing South Carolina in the case. He opposed the intervention of the private entities into the dispute.

Roberts called the ruling “unprecedented.”

“[T]his Court has never before granted intervention in such a case to an entity other than a State, the United States, or an Indian tribe,” Roberts wrote. “Never. That is because the apportionment of an interstate waterway is a sovereign dispute, and the key to intervention in such an action is just that — sovereignty.”

A third entity, the City of Charlotte, was found not to have met the standard, which McMaster said was a positive step for South Carolina’s argument in that Charlotte is the largest consumer of water along the basin as a whole and in North Carolina in particular. The court ruled that the State of North Carolina could represent Charlotte’s interests in the case.

The 225-mile Catawba River provides drinking water for more than one million people and supplies electrical power to more than two million people. In 2007, South Carolina filed suit against North Carolina for taking more water from the river than its equitable share due to drought conditions in North Carolina.

A date has not yet been set for a hearing of the case.