Decades of negotiations between the tribe and Arizona over water rights have proven fruitless. The court case was the Navajo Nation’s bid to accelerate the process and secure water for its reservation.

More than 150 years after the Navajo Nation signed treaties with the United States establishing its reservation and recognizing its sovereignty, the country’s largest tribe still struggles to secure the water guaranteed by those agreements.

In a 5-4 decision, the court denied the Navajo Nation’s request that the federal government be forced to act in a timely manner to help the tribe quantify, settle and access its water rights… … Writing for the majority, Justice Brett Kavanaugh said the tribe’s treaties do not impose “a duty on the United States to take affirmative steps to secure water for the Tribe.”

Link to the PDF going over the 5-4 SCOTUS decision.