The federal government can't make rules for the ways Las Vegas-style games are played at Indian casinos, an appeals court ruled Friday in a blow to efforts to regulate the booming, $22 billion tribal gambling industry.

The decision by a three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit arises from a dispute in Arizona between the Colorado River Indian Tribes and the National Indian Gaming Commission, the federal agency that oversees Indian casinos.

The commission tried in 2001 to audit the tribe's casino in Parker, Ariz., to ensure compliance with recently enacted federal standards for how games like blackjack and slot machines are run. The tribe objected, contending the commission was overstepping its authority under the National Indian Gaming Regulatory Act.

A federal district court sided with the tribe, and the appeals court agreed in an 11-page ruling. While federal law gives the gaming commission some authority over games like lotto and bingo on Indian land, the big moneymakers like blackjack and slots classified as "Class III" games are outside the commission's jurisdiction, said the ruling written by Judge A. Raymond Randolph.

"What is the statutory basis empowering the commission to regulate Class III gaming operations?" the ruling asked. "Finding none, we affirm" the lower court's decision.

Tribes can open Las Vegas-style casinos only after they sign a "compact" with their state's governor, and the court asserted there was no federal role in regulating the game-playing.

Tribal gambling has grown explosively since Congress established the legal framework for it in 1988, and there are now more than 400 Indian gambling facilities operated by 223 Indian tribes in 28 states.

With the growth have come conflicts as tribes have asserted their sovereignty as independent governments. Local and state governments have sought to sketch out some authority, and the federal government increasingly has attempted to regulate aspects of Indian gambling from labor to slot machine standards.

The National Indian Gaming Association welcomed the ruling as a victory for tribal sovereignty.

"Today, the federal court of appeals told us what Indian tribes always knew it is not the NIGCs job to establish federal regulations that override the sovereign decisions of tribes and states made through Class III gaming compacts," the association's chairman, Ernest Stevens, Jr., said in a statement.

Officials with the National Indian Gaming Commission did not immediately return calls seeking comment.