Lanni, 65, announced Nov. 13 he would retire from the company’s day-to-day operations but would accept a role as an outside director.

The retirement is effective Sunday. Company President Jim Murren was elected to fill the casino operator’s chairman and CEO positions Monday.

At the same time as Murren’s appointment, Lanni was elected to an outside director’s position. On Tuesday he informed the company he would not accept the post.

On the day Lanni announced his departure, questions arose surrounding his academic credentials. Some company materials through the years have said Lanni had a master’s of business administration in finance from the University of Southern California. The university said Lanni never earned an MBA at the school.

Last week, the Review-Journal reported that gaming authorities in Nevada, New Jersey and Michigan were checking Lanni’s educational background.

Peter Aseltine, spokesman for the New Jersey Division of Gaming Enforcement, where MGM Mirage co-owns the Borgata in Atlantic City with Boyd Gaming Corp., said regulators were “looking into the situation.”

New Jersey gaming regulators have yet to issue a ruling on the suitability of MGM Mirage’s joint venture partnership in Macau with Hong Kong businesswoman Pansy Ho, the daughter of controversial billionaire Stanley Ho. The company and Pansy Ho are 50-50 partners in the MGM Grand Macau, which opened last December.

Nevada gaming regulators ruled last year that Pansy Ho was a suitable business partner for MGM Mirage. However, New Jersey gaming officials still have the matter under advisement.

Several gaming sources, speaking on condition of anonymity, said Lanni’s decision to step away from the company was because of New Jersey. If Lanni included false information about his education in any jurisdiction where MGM Mirage operates, regulators could deny him a seat on MGM Mirage’s board or question his decisions.

Aseltine declined to discuss details of an investigation with the Review-Journal.

On Tuesday, Lanni resigned his seat on the board of directors of KB Home. The position with the home builder was Lanni’s only corporate board position outside of MGM Mirage.

Lanni also serves on the board of trustees for the Ronald Reagan Presidential Foundation, the Board of Overseers of the Keck School of Medicine at the University of Southern California, the board of trustees at Santa Clara University and the Del Mar Thoroughbred Club.

Lanni joined the then-MGM Grand Inc. as president, CEO and a member of the board in June 1995 and steered the company’s massive growth over the past 13 years, including the $6.4 billion purchase of Mirage Resorts in 2000 and the $7.9 billion buyout of the Mandalay Resort Group in 2005. Lanni is also considered responsible for implementing MGM Mirage’s highly recognized corporate diversity efforts.

Before joining MGM Mirage, Lanni spent 18 years as a senior executive at Caesars World, including 14 years as president and chief operating officer.

Lanni had a base salary of $2 million in 2007, but received total compensation of $12.7 million, which included incentives and perks.

Contact reporter Howard Stutz at hstutz@reviewjournal.com or 702-477-3871.