The US Supreme Court [official website] ruled [opinion, PDF] unanimously Thursday in Tarrant Regional Water District v. Herrmann [SCOTUSblog backgrounder] that the Red River Compact [materials] does not preempt Oklahoma water laws. The Red River Compact regulates water rights from the Red River among the states of Texas, Oklahoma, Arkansas and Louisiana. Tarrant Regional Water District, a Texas agency, claimed that it was entitled to divert water from within Oklahoma because the compact preempts Oklahoma statutes that restrict such diversions. Alternatively, Tarrant argued that the Oklahoma laws were unconstitutional restrictions on interstate commerce. In an opinion by Justice Sonia Sotomayor, the court held that Tarrant's claims lack merit: "The Red River Compact does not pre-empt Oklahoma's water statutes because the Compact creates no cross-border rights in its signatories for these statutes to infringe. Nor do Oklahoma's laws run afoul of the Commerce Clause." The court affirmed the ruling [text] of the US Court of Appeals for the Tenth Circuit.
The court heard oral arguments [JURIST report] in the case in April. The attorney for Tarrant argued that the Red River Compact clearly allowed Texas to use the Red River as it saw fit, and "Oklahoma is now trying to back out of that bargain." An attorney for Rudolf John Herrmann, representing the Oklahoma Water Resources Board, stated that through a strip called Shawnee Creek, all of the Red River in Texas, and Lake Texoma, "Texas users draw water, quite a lot of water," and thus should not need to dip into Oklahoma territory.