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Steve Chiotakis: Later this morning, the Supreme Court hears a case that might weaken longstanding investor protections in the mutual-fund industry. Marketplace's Steve Henn reports.

Steve Henn: The case is called Jones v. Harris. And it could end up re-writing the rules that protect more than 93 million Americans with mutual funds from unreasonably high fees.

It began when three investors sued their mutual fund company arguing that the fund's investment adviser was over-charging them. They say they paid higher fees than institutional investors did and that's not fair.

William Birdthistle: That's the comparison we need.

William Birdthistle is a law professor at Chicago Kent Law School.

Birdthistle: Institutional investors are very sophisticated. They're watching very closely and they can take care of themselves very well.

Birdthistle believes many small investors are routinely overcharged.

But Paul Stevens at the Investment Company Institute says costs associated with smaller accounts are proportionally higher than those for large institutional investors.

PAUL STEVENS: It's not even an apples to apples comparison, it's kind of an apples to watermelons comparison.

And he says if small investors don't like the fees they're charged, they can always take their money somewhere else.

In Washington, I'm Steve Henn for Marketplace.