For more than a century, since Winters v. United States, 207 U.S. 564 (1908), the Supreme Court has recognized that when the United States establishes a Native reservation, it impliedly reserves sufficient water rights to support that reservation. But many of these Winters rights, like those held by the Navajo Nation, remain unadjudicated and unquantified, creating uncertainty for junior right holders. A recent decision from the Ninth Circuit Court of Appeals confirms that the United States cannot ignore Winters rights held by tribes just because they have not been adjudicated..