(Adds details of ruling and background, paragraphs 4-10)

By Lawrence Hurley

WASHINGTON, June 25 (Reuters) - The U.S. Supreme Court on Friday ruled that federal COVID-19 relief funds can go to specially created corporations for Native Alaskans even though they are not officially recognized as tribal governments in a case pitting groups of indigenous Americans against each other.

The justices ruled 6-3 that the native corporations are eligible to receive funding intended for tribal governments under the 2020 Coronavirus Aid, Relief and Economic Security Act, known as the CARES Act. About $533 million in funding hinged on the case's outcome.

Three groups of Native American tribes from other parts of the United States sued in federal court in Washington in April 2020 seeking to prevent what are known as Alaska Native corporations from receiving any of the funds. Among the challengers were the Navajo Nation, the Confederated Tribes of the Chehalis Reservation and the Cheyenne River Sioux Tribe.

Writing for the court, liberal Justice Sonia Sotomayor the ruling "affirms what the federal government has maintained for almost half a century." Conservative Justices Clarence Thomas and Neil Gorsuch were joined by liberal Justice Elena Kagan in dissent.

The CARES Act set out $8 billion to be distributed to tribal governments, which were defined as the "governing body of an Indian tribe" based on the definition described in a 1975 federal law called the Indian Self-Determination and Education Assistance Act, which does mention the Alaska corporations.

The U.S. Court of Appeals for the District of Columbia Circuit last year reversed a lower court's ruling that had favored the federal government and the corporations, prompting the appeal to the Supreme Court, which heard arguments https://www.reuters.com/world/us/us-supreme-court-sympathetic-native-alaskans-covid-19-aid-dispute-2021-04-19 in April.

The 12 corporations were established to help Native Alaskans thrive after Alaska achieved statehood in 1959. They have become successful and diversified businesses with interests in such areas as oil and gas drilling, real estate and construction. In 2017, they had a combined revenue of $9.1 billion. The corporations also provide various social services for Native Alaskans.

The corporations were created under a 1971 federal law that sought to address land claims and provide economic benefits to Native Alaskans without allocating land to tribal governments. Federal funding and land, including mineral rights, were given to the new regional corporations.

This law also set up separate Alaska native village corporations on a smaller scale. Native Alaskans received stock in the corporation set up where they lived.

(Reporting by Lawrence Hurley; Editing by Will Dunham)