The U.S. Supreme Court rejected a lower-court ruling that made it harder for individual shareholders to sue a mutual fund investment adviser for excessive fees.

The high court unanimously upheld a standard that has been in place since the early 1980s to decide the fairness of fund fees.

The case has been closely watched by the $11 trillion mutual fund industry. The Supreme Court endorsed the standard in place since the early 1980s in deciding the fairness of fees.

The justices set aside a ruling by a federal appeals court in Chicago that adopted a tough new standard by requiring shareholders to show that an adviser had misled the fund's directors who approved an excessive fee.

The case involved a lawsuit by three shareholders of the Oakmark Funds. Harris Associates LP of Chicago serves as the funds' investment adviser, deciding which stocks to buy and sell. Harris is an indirect subsidiary of Natixis SA affiliate Natixis Global Asset Management LP.

A lawyer for the three investors said Harris charged fees twice as high for individuals as for large institutional clients like pension funds. An attorney for Harris defended the fees as in line with those charged by similar mutual funds.

About 92 million individual investors in 52.5 million households own mutual funds. Those investors can select from more than 8,000 funds offered by more than 700 advisory firms, according to statistics from the mutual fund industry trade group.

In the standard set out in a 1982 court ruling, fees have been deemed to be excessive only if they are so high they could not be the result of arm's-length negotiations and bear no reasonable relationship to the services provided.

Justice Samuel Alito wrote in the court's 17-page ruling that a consensus has developed regarding that standard, and it has been used by federal courts and the U.S. Securities and Exchange Commission.

Alito said it has proven to be a workable standard for nearly three decades.

(Reporting by James Vicini, Editing by Gerald E. McCormick and John Wallace)