[JURIST] Montana filed a lawsuit Thursday against Wyoming [JURIST news archives] in the US Supreme Court [official website; JURIST news archive] for allegedly violating a 1950 agreement allocating water rights [Wikipedia backgrounder] to two tributaries of the Yellowstone River. In a motion, complaint and brief [PDF text], Montana Attorney General Mike McGrath asserted that Wyoming had breached the Yellowstone River Compact [DOC text and summary] by failing to keep consumption of water from the Tongue and Powder rivers within the compact's limits – specifically, by allowing water storage facilities to be built and irrigation to be expanded. Montana claims that, as a result of Wyoming's actions, its ranchers, farmers and other water users are suffering "substantial and irreparable injury." McGrath asked the court to order Wyoming to abide by the compact and to award Montana damages, interest and costs. North Dakota [JURIST news archive], the third signatory to the compact, is also named as a defendant, but Montana is not seeking relief from that state.

Montana filed the lawsuit after the Yellowstone River Compact Commission [official website] last month rejected a resolution that would have adopted Montana's interpretation of the compact. "In the West, a deal is still a deal," Montana Gov. Brian Schweitzer [official website] said Thursday in a press release [text]. "Wyoming signed a compact that said Montana would get its fair share of water and Wyoming has not been holding up its end of the deal." In a statement [text] responding to the lawsuit, Wyoming Gov. Dave Freudenthal [official website] said his state has "strictly honored" the compact. The statement continued:

Prior to 2004, Wyoming and Montana agreed on how the compact operated. Since 2004, Montana has been agitating for a fight. I guess they finally threw the first punch. I am confidant [sic] that Wyoming will prevail on this claim, but I am disappointed that Wyoming will be forced to expend millions of dollars to defend a claim that has no merit.

The lawsuit was filed directly in the Supreme Court because Article III, Section 2, of the US Constitution [text] gives the court original jurisdiction over cases "in which a state shall be party." By statute [text], Congress has made the Supreme Court's jurisdiction over "all controversies between two or more States" exclusive, meaning no other federal court may consider such cases. According to the treatise Supreme Court Practice [text], the court customarily appoints a special master [Cornell LII backgrounder] to hear original jurisdiction cases in which the facts are disputed. Once the special master makes findings and recommendations, the court hears oral arguments as it would in a typical appellate case. Under a Supreme Court rule [text], Wyoming now has 60 days to file an opposing brief. AP has more. The Missoulian has local coverage. SCOTUSBlog has additional coverage.

This report was prepared in partnership with the Pittsburgh Journal of Environmental and Public Health Law.