NEW ORLEANS — Who owns "Who Dat?"

Some T-shirt makers are asking that question after they were hit with cease-and-desist letters from the NFL demanding that they stop selling shirts with the traditional cheer of New Orleans Saints fans.

The National Football League says the shirts infringe on a legal trademark it owns. Separately, two brothers and longtime Saints fans claim they own the phrase, which was around before the long-downtrodden team's inception in 1966.

The league said yesterday it's not trying to exclude all uses of Who Dat and the fleur-de-lis logo — just when either is used in combination with other Saints trademarks, like their fleur-de-lis logo and uniform designs.

The chant — "Who dat say dey gonna beat dem Saints" — is often shortened to "Who Dat" on shirts and signs and has been a mainstay at the Superdome since the 1980s. Saints fans, still jubilant after the Saints' win over the Minnesota Vikings for their first Super Bowl appearance, have voiced their dismay on radio talk shows, blogs and Web site posts. Many say it's something that simply can't be owned.

"How can they put a trademark on something that's been around for 150 years?" said Robert Lauricella, a 50-year-old oil field sales representative. "Just because the Saints have made the Super Bowl, why does everybody have to make a buck?"

Shirts bearing the Saints cheer are big business as the team prepares for the big game against the Indianapolis Colts in Super Bowl XLIV on Feb. 7 in Miami.

Lauren Thom, owner of the Fleurty Girl T-shirt shop in New Orleans, said Thursday that she recently received a letter from the NFL demanding that she quit selling "Who Dat" shirts.

"I don't mind paying royalties," Thom said. "I just don't know who owns 'Who Dat' or whether it's in the public domain."

The NFL doesn't cut much slack when it believes it owns a trademark. This case is no exception.

In an e-mail, league spokesman Brian McCarthy said the NFL has sent a handful of letters in the past year asking vendors to stop selling "Who Dat" merchandise. The unlicensed shirts led fans to believe the Saints endorsed the product, he said.

"This helps protect the local businesses that are selling legitimate Saints merchandise and also the local printers that are making the licensed Saints apparel," he said.

Meanwhile, WhoDat Inc., controlled by longtime Saints fans and brothers Sal and Steve Monistere, also claims rights to the phrase.

In 1983, Steve Monistere produced the song "Who Dat Say They Gonna Beat Dem Saints" with Aaron Neville and several Saints players.

In a statement Thursday, WhoDat Inc. said that before that recording, there were no branded items with the motto. The brothers said the company has the only federal trademark for "Who Dat." Steve Monistere said he and his brother were at the Saints' first game in 1967 and have been fans through all the ups and downs — mostly downs, of course.

Storyville shop co-owner Gabriel Harvey pulled his "Who Dat" shirts after getting letters from the NFL and WhoDat Inc.

"It seems unclear who, if anyone, owns it," Harvey said. "A lot of people believe it belongs to the city and the people."

Two members of Louisiana's congressional delegation — Republican Sen. David Vitter and Democratic Congressman Charlie Melancon — took public umbrage at the NFL.

Vitter wrote NFL Commissioner Roger Goodell, urging the league to concede that "Who Dat" is in the public domain. Otherwise, Vitter said he will print and sell T-shirts with "WHO DAT say we can't print Who Dat!" on them.

"Please either drop your present ridiculous position or sue me," Vitter wrote.

Later yesterday, NFL vice president Jeffery Miller told Vitter in a letter that the league is narrowly targeting Who Dat products "only when those products contain or are advertised using other trademarks or identifiers of the Saints.

"This is consistent with steps the NFL has taken in the markets of the NFL's other 31 member clubs when infringements are identified," Miller said.

Melancon provided a link — headed "No One Owns WHO DAT" — on his Twitter page to a petition encouraging the NFL to back off.

The "Who Dat" chant's origins are somewhat murky. Some historians say it came about in the days of late 19th-century minstrel shows and later showed up in vaudeville routines. In 1937's "A Day at the Races," the Marx Brothers perform a number — in blackface — called "Who Dat Man."

"Who Dat" also is used in a 1938 MGM cartoon — now seldom seen because of its racially offensive nature — called "Swing Wedding," which featured frog caricatures of black entertainers such as Ethel Waters, the Mills Brothers, Louis Armstrong and Cab Calloway.

It's been yelled at high school and college games, and fans of the Cincinnati Bengals are known to chant "Who Dey?"

Glenn Lunney, a Tulane University Law School professor specializing in intellectual property, said a trademark is different from a copyright or patent and doesn't necessarily have to be original. For example, computer and iPod manufacturer Apple trademarked the familiar, centuries-old fruit, he said.

"You can take a word and by applying it to goods or services get people to think about your goods or services," and get commercial rights, he said.