The four major U.S. professional sports leagues could reap a combined $4.2 billion annually as a result of legal sports bets, most of it indirectly from increased fan engagement, according to a casino industry survey released on Thursday.

The findings could fuel a long-simmering feud between the gaming industry and American sports leagues, who want a share of the gambling revenue as U.S. states begin to legalize sports betting.

The survey showed leagues stand to benefit even without taking a cut of wagers. The National Football League is likely to make the most, with a projected $2.33 billion of additional annual revenue, according to the study seen by Reuters. The rest would go to Major League Baseball, the National Basketball Association and the National Hockey League.

For years, the leagues fought states’ efforts to legal sports bets, arguing it would lead to game fixing. But in May, the U.S. Supreme Court threw out a federal ban against sports betting, paving the way for any state to legalize, regulate and tax the activity.

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