A district court judge in Boise is set to hear a case on Tuesday morning regarding the question of whether federal land agencies can retain water rights on public land in Idaho for livestock to drink, even if the agencies don’t own the cattle.

The case stems from a 30-year process of sorting out water rights in the Snake River Basin, which ended in 2014.

During this adjudication, some ranchers contested the ability of the Bureau of Land Management and the Forest Service to hold water rights for cattle, known as stockwater rights. Because the agencies didn’t own the animals, the ranchers argued, they weren’t the ones putting the water to a “beneficial use,” a requirement under state water law.

In 2007, a state supreme court case ruled in favor of ranchers at Joyce Livestock Co. in Owyhee County who had sued over this issue. Over the following years, through several legislative measures and Department of Water Resources orders, Idaho began pressuring the federal agencies to give up some of these stockwater rights.

Two years ago, the U.S. The Department of Justice sued in protest, arguing that the new Idaho laws couldn’t be lawfully enforced against the U.S. because they violated the Supremacy Clause of the Constitution and federal sovereign immunity.

It also argued Idaho was discriminating against the federal government by targeting the roughly 25,000 instream stockwater rights on federal grazing allotments and not those on private or state lands.

Marie Callaway Kellner, a professor at the University of Idaho College of Law, said the government also feared broader implications, like its ability to manage for multiple uses on federal lands.

“There’s a sense,” she said, “that if it loses the ability to manage how the water is used, it will lose the ability to manage how grazing happens on these lands.”

Clive Strong, who was the Office of the Idaho Attorney General’s lead attorney during the Snake River Basin Adjudication, said, on the other hand, if it’s determined that the U.S. has a broad exemption from state water law, that could affect Idaho’s ability to fully regulate water rights under its rules like “first in time, first in right,” and the requirement to put water to beneficial use.

“This case is important,” Strong said, “because it is testing the boundaries of that deference to state water law.”

The state also replied that the dispute had already been argued before the Supreme Court in the Joyce Livestock case.

The Idaho Legislature, the Idaho Farm Bureau Federation and ranchers including Joyce Livestock Co. joined in to intervene in the case.

The court is considering motions for summary judgment from both sides.

Find reporter Rachel Cohen on Twitter @racheld_cohen

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