WASHINGTON -- Senators from both parties warned the National Football League on Thursday to get rid of a four-decade-old TV "blackout'' rule or risk congressional action to restrict the league's lucrative antitrust exemption, which allows NFL teams to negotiate radio and television broadcast rights together.

The blackout rule, which bars home games from being televised in a local market if they have not sold out, is unfair to fans who have helped the league reap billions of dollars in revenue from broadcast rights to games that are among the most-watched programs on TV, lawmakers said.

In return for their loyalty, "fans in the public are often treated like a fumbled football,'' said Sen. Richard Blumenthal, D-Conn. "When places like Buffalo, New York, fail to sell out its 74,000-person stadium, the Bills game is blacked out for local fans.''

"The simple fact is that these rules only serve to benefit sports leagues and their member teams at the expense of the hardworking fans who support them so loyally through their money, time and passion."

The Federal Communications Commission voted this fall to stop enforcing the NFL's blackout policy, but the action did not end blackouts, which are written into the NFL's private contracts with broadcast and cable companies.

Blumenthal and other lawmakers at a Senate Judiciary Committee hearing said Thursday the blackout rule has long outlived its usefulness. The rule was adopted in the 1970s to encourage ticket sales at NFL games, which now routinely sell out at stadiums across the country.

"The simple fact is that these rules only serve to benefit sports leagues and their member teams at the expense of the hardworking fans who support them so loyally through their money, time and passion,'' said Sen. John McCain, R-Ariz.

During last year's NFL playoffs, fans of the Cincinnati Bengals, Indianapolis Colts and Green Bay Packers came close to experiencing blackouts when those games had not sold out just days before kickoff, McCain said. The blackouts were averted when local businesses bought tickets to bring the total above the NFL's required threshold.

A bill co-sponsored by Blumenthal and McCain would revoke the league's antitrust exemption unless it removes the blackout rule.

The senators made it clear at Thursday's hearing that they would prefer not to enact a bill. Blumenthal and other lawmakers urged the NFL to act on its own.

"I think they'd become heroes rather than the opposite, which they are now,'' Blumenthal said.

Gerard Waldron, a lawyer who represents the NFL, said the proposed bill would harm the people it intends to help -- the fans -- by undermining "the complex business and legal structure that allows the NFL to be the only professional sports league that offers all of its regular-season game to viewers at no charge'' through over-the-air broadcasts.

Without the certainty of paid attendance provided by a blackout rule, NFL games are likely to migrate from free broadcast TV to pay TV such as cable and satellite, Waldron said.

The bill also aims fix a problem that largely does not exist, Waldron said, noting that no NFL games have been blacked out this season and only two games were blacked out in 2013. Without threats of a blackout, advertisers may not be willing to spend as much money to sponsor NFL games, he said.

"The key factor that distinguishes the NFL from other types of programming is its ability consistently to deliver a mass audience at a fixed time,'' he said.

But David Goodfriend, chairman of the Sports Fans Coalition, an advocacy group, said the government should not support "anti-fan activities'' by professional sports leagues such as the NFL.

"When a sports league receives a public benefit'' such as the antitrust exemption and other subsidies, "the fans should get a fair return or the subsidy should go away,'' Goodfriend said.

Lawmakers at the Thursday's hearing appeared generally sympathetic to Goodfriend's argument, but two Minnesota senators told him should have done a better job researching his audience. A Green Bay Packers fan, Goodfriend wore a Packers tie to the hearing -- which was noted by Democratic Sens. Amy Klobuchar and Al Franken of Minnesota.

"It might not have been your smartest move, given that half of the senators here are from Minnesota,'' Klobuchar told Goodfriend.