As investors, fans, regulators, bookies and others track the spread of sports betting in the U.S., the National Football League on Thursday continued to call for new federal regulations on this growing industry.

“We are asking for core standards to protect the integrity of our game,” said Jocelyn Moore, the NFL’s executive vice president for communications and public affairs, speaking at a hearing on Capitol Hill.

The NFL is asking for new nationwide laws that feature limits on wagers on specific actions occurring during games — including how many flags are thrown by referees, or how many yards quarterbacks throw for, what are known as prop bets. These types of bets are more susceptible to match-fixing moves, Moore said. There also should be a ban on bets by athletes, coaches, referees and employees of sports organization, the league reckons.

Thursday’s hearing before a House subcommittee comes about four months after a Supreme Court decision that opened the door for states to allow betting on sporting events, invalidating a federal law that prohibited such wagers in most of the U.S. The May ruling has spurred American casino operators, British bookmakers and other companies to brace for more business and make deals.

In her testimony, the NFL’s Moore cited former Sen. Bill Bradley’s concerns about sports betting that he voiced nearly 30 years ago. Bradley, a basketball legend before he switched to politics, back then warned that widespread betting could turn sports into “the gamblers’ game and not the fans’ game, and athletes would become roulette chips.”

There should be a national sports-betting framework with substantial safeguards for consumers, as well as tools for law enforcement and standards to protect the NFL’s content and intellectual property, according to Moore. The league also wants lawmakers to limit sports betting to adults aged 21 and up.

Estimates for the U.S. sports-betting market’s possible annual size range from$100 billion to $400 billion. Analysts have said U.K. gambling companies such as William Hill PLC and Sportingbet parent GVC Holdings could offer a good way for investors to ride the spread of sports betting in the U.S., as some had prepared for the Supreme Court ruling and boast considerable American operations.