Over 150 years ago, treaties between the U.S. and Navajo Nation promised the tribe a “permanent home,” but today, roughly a third of the reservation’s 175,000 people lack access to running water and water rights.  The Navajo Nation has filed lawsuits to reclaim their water rights over the Colorado River for decades but has yet to succeed. Climate change is shrinking the overused Colorado River basin, making its water rights more valuable, and contentious.

Four states, along with major water users in California and Arizona, prompted the U.S. Supreme Court to review a lower court decision that sided with the Navajo Nation, requiring the U.S. to honor treaties signed after the Navajo were forcibly removed from their ancestral lands. The U.S. Supreme Court’s decision is expected to be a landmark one in Native American law and will impact the water source for around 40 million people.

“The Nation is still waiting for the water it needs,” the tribe writes in court papers, asking the justices to agree with their “breach-of-trust claim” in federal court. The Navajo Nation’s opponents to their plea for water rights argue the Navajo Nation are not able to file lawsuit in the first place, since the Supreme Court has said they have exclusive jurisdiction over disputes involving the Colorado River .(AP, NPR, Politico Pro $)