On Friday, the other leagues stood firm in their defense of Paspa. Brian McCarthy, a spokesman for the N.F.L., said Silver’s view “doesn’t change our stance that has been articulated for decades: no gambling on N.F.L. games.”

Bill Daly, the deputy commissioner of the N.H.L., was more nuanced. “That was Adam’s opinion, and certainly one he and the N.B.A. are entitled to,” Daly wrote in an email. “That does not mean we share it. I think there are several assertions he relies on that we might question, or certainly would want to test further, and there are other considerations not mentioned that we think are relevant. It is a complex issue and, at least from our perspective, one that does not lend itself easily to a simple ‘agree’ or ‘disagree.’ ”

Those in the gambling industry, of course, are cheering Silver on. “We agree with Commissioner Silver that a legal and regulated sports betting industry, like we have in Nevada and elsewhere in the world, is the best way to protect the integrity of sporting events,” said Joe Asher, the chief executive of William Hill US in Nevada.

Though any immediate shift in federal gambling laws is a long shot, leagues have in the past changed their views when money was involved. For years, leagues did not take money from liquor companies that wanted to advertise in arenas and stadiums. That opposition dissolved a few years ago when the recession constrained advertising.

Leagues that once opposed the scalping of tickets have done deals with Ticketmaster, StubHub and other online ticket marketplaces in the name of convenience and security for fans. The leagues have leapfrogged Slingbox, a service that allows fans to watch out-of-market games, by selling cable TV and Internet packages that show every game of every team.