As the quarterback of the Dallas Cowboys, Tony Romo is a lightning rod for many things, starting with his team’s inability to make it to the Super Bowl, and the pop stars he has dated.

The N.F.L. thrust him deeper into the spotlight this month when it reiterated its rules that prohibit players from taking part in events that are held at or are sponsored by casinos.

This led the National Fantasy Football Convention to cancel an event it planned to hold in July at a convention center attached to a casino in Las Vegas. It also led Romo, who promoted the event, and other players, like his teammate Dez Bryant, who had planned to attend, to call the N.F.L. greedy and jealous.

“It’s like when you’re in high school and you don’t get invited to the party, it makes you feel bad,” Romo told “The Herd with Colin Cowherd” on ESPN Radio. “If they really wanted to just be a part of it, all they had to do was just call and ask.”

The N.F.L. insists that it has no problem with fantasy football, which it has embraced. Rather, it wants to preserve the integrity of its game.

After the league clarified its rules, Bo Brownstein, the founder of the Fantasy Sports Combine, which will hold its own event next month in Las Vegas, removed several players, including Brandon Marshall and Von Miller, from its program.

“It’s not a popular position, but they are protecting a major business,” Brownstein said of the N.F.L.

But the N.F.L.’s stance has not persuaded many fans who are less sympathetic to the legal distinction between games of skill (fantasy sports) and games of chance (gambling). To many of them, the distinction is arbitrary and the ban on sports gambling is outdated and intellectually dishonest.

“It’s the biggest hypocrisy in sports,” said Scott Andresen, a sports and entertainment lawyer who teaches at Northwestern. “The N.F.L. and other leagues are in opposition to legalized sports gambling because they haven’t quite figured out how to monetize it. Once they do, they’ll all be on board.”

Andresen and other critics note that the N.F.L. already does business with casinos, and contend that trying to keep players from working in casinos is impossible because gambling and gamblers are everywhere. As Andresen put it: “Mobsters can travel, too.”

Indeed, Tim Donaghy, the former N.B.A. referee who pleaded guilty to conspiring with gamblers, was not courted in Las Vegas. 

Sports leagues have long wrestled with how to keep gamblers at bay while also making money for their owners. Leagues bar players from working at or with a casino, yet those same casinos advertise in stadiums around the country. All but five N.F.L. teams play in markets where legal casinos operate, according to Sara Rayme, a spokeswoman for the American Gaming Association.

“It is only a matter of time before such thinking in organizations like the N.F.L. evolves and acknowledges the reality that gaming, like professional sports, is a form of mainstream entertainment,” she said in a statement.

The N.F.L. and other leagues also let teams work with state-run lotteries and accept advertising money from casinos. NFL RedZone and DirecTV’s Sunday Ticket were created not just to attract more cable and satellite subscribers, but also to satisfy fans who bet on the players and games.

Fantasy football has blurred the lines further. The N.F.L. likes it because it generates interest in games that fans might otherwise ignore. Analysts discuss fantasy football on NFL Network, and the league has hosted a fantasy draft week. 

“We generate a lot more fan engagement,” said Jason Robins, the chief executive of DraftKings, which runs daily fantasy tournaments and has deals with five N.F.L. teams. Fans, he said, watch “blowouts on ‘Monday Night Football’ because it could affect their fantasy scores.”

But the N.F.L. has been more cautious about working with daily fantasy sports operators than Major League Baseball, which has an equity stake in DraftKings, and the N.B.A., which has a four-year exclusive deal with DraftKings’ rival, FanDuel. The N.F.L. does not have a leaguewide deal, but it lets teams accept advertising from daily fantasy game providers.

The league’s measured approach may be because daily fantasy, in which players draft lineups whenever there is a new slate of games, is closer to gambling than seasonlong fantasy. Some have compared the games to day trading and investing.

Both, ultimately, are betting on stocks, which is why some fans view fantasy football as no worse than playing poker in a casino or in a basement with friends. That logic will continue to ensnare the N.F.L.

“You have this space that can both positively and negatively affect your brand,” said Craig Amazeen, senior vice president at Scout, a digital sports network and the home of the Official Fantasy Football World Championships. “They are trying to dance on a dance floor, but the boundaries of the floor keep changing.”