The Supreme Court on Wednesday seemed open to the possibility of making it harder for investors to join together to sue corporations for securities fraud — but maybe not as hard as companies that have to defend such lawsuits would like.

Any change in the standard for green-lighting class-action lawsuits could have a chilling effect on shareholders who bring the cases, which have generated an estimated $73 billion in settlements since 1997. Investor groups say class actions help curb corporate abuse and market fraud, while opponents claim they extort money from corporations and create a windfall for plaintiff’s lawyers.