LOS ANGELES (AP) — One of the most valuable pieces of baseball memorabilia — a copy of the 1876 National League constitution that established business practices that remain the norm today — is at the center of a legal dispute between the family of a late baseball executive and an auction house they say is holding it hostage.

Mary Elizabeth Fleig, the 92-year-old widow of Fred Fleig, and a company owned by his son-in-law, Keith Nadel, filed a lawsuit Wednesday in Los Angeles County Superior Court against SCP Auctions.

The two sides were working together last May to sell the papers that had been among Fred Fleig's belongings when he died in 1979, a year after he retired as the National League's secretary and treasurer. But after ads and an Associated Press story appeared about the auction, Major League Baseball claimed it was the rightful owner and the sale was stopped.

The league and the Fleig family later quietly reached a settlement for joint ownership of the papers, but the lawsuit filed Wednesday by Los Angeles law firm Greenberg Glusker alleges that SCP Auctions has refused to relinquish control of the document "unless and until it is paid a preposterous 25 percent 'commission' that is not provided, permitted or justified" by the auction agreement, which only calls for 5 percent.

"SCP's outrageous demand constitutes civil extortion," the suit states.

The lawsuit seeks the immediate return of the papers along with unspecified damages. An email sent seeking comment from the auction company was not immediately returned.

Baseball historians say the document, largely the work of Chicago White Stockings owner William Hulbert, was essential in giving a suspicious and disreputable game respectability in the late 19th century.

"It is this model that gave birth to every professional sports league that followed, from football to basketball to European football," John Thorn the official historian of Major League Baseball, told the AP last year.

The papers had been among the belongings in 10 boxes sent from Fleig's National League office to his Danville, California, home after his 1978 retirement.

He died the following year, and National League President Chub Feeney had given the family the right to any memorabilia that he happened to have, leading the family to believe it could rightfully sell the documents.

Two years ago, a similar set of papers establishing the rules of modern baseball sold for more than $3 million, and experts believed the constitution at auction could go for even more, perhaps surpassing a Babe Ruth jersey that once sold for $4.4 million.

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