The investigation into Richardson was first reported by ESPN.
The news of the investigation followed a report Monday that a former NFL Network wardrobe stylist had filed an amended complaint in a lawsuit that accused employees at the network of sexual harassment and assault. Six current and former NFL Network employees, including five former N.F.L. players, have been suspended.
N.F.L. Commissioner Roger Goodell said Wednesday at an owners meeting in Dallas that the league would investigate the claims in the lawsuit.
The Panthers announced that the team had hired the law firm Quinn Emanuel Urquhart & Sullivan to look into the allegations against Richardson, and that Erskine Bowles, a Clinton administration official and a minority owner of the team, would oversee the investigation.
Richardson, 81, has largely dropped out of view in the past two years. The turning point came when the league’s owners voted to let the Rams move from St. Louis to Los Angeles in 2016. He had recommended that the Oakland Raiders and San Diego Chargers be allowed to move there. (The Chargers moved to Los Angeles this year.)
Richardson did not attend Wednesday’s owners meeting, where a $200 million contract extension for Goodell became official, but he did send the six owners on the commissioner’s compensation committee a letter that called for more transparency in how the committee did its work.
“We should not manage to avoid criticism, but work passionately to provide positive outcomes,” Richardson wrote. “Nothing less should be expected or accepted.”
Richardson played two seasons in the N.F.L., in 1959 and 1960. He later became a restaurant magnate, running a food service company that worked with the Hardee’s chain. He was awarded an N.F.L. expansion franchise in 1993, and the team began play in 1995.
It is unclear how independent the investigation will be because it is being led by a minority owner who is presumably close to Richardson. In other investigations of sports franchise owners, the league itself has taken the lead, such as when the N.B.A. looked into racist remarks made by Donald Sterling, then the owner of the Los Angeles Clippers.
The N.F.L. updated its personal conduct policy in 2014, expanding the guidelines and penalties to cover not just players, but all employees. The league also set up its own investigative unit to look into claims of misconduct off the field.
Joe Lockhart, an N.F.L. spokesman, declined to comment on the investigation involving Richardson.