The US Supreme Court on Tuesday closed the courtroom door on one form of big investor class-action lawsuits, siding with US business and dismissing the claims of some shareholder groups.

The court, which ruled unanimously, appeared eager to close a loophole in federal securities laws that could have led to an explosion of investor class-action litigation. The justices ruled that a federal law prevents people who hold stocks ? rather than buying and selling them ? from bringing large class-action lawsuits claiming they have suffered losses because of a stock fraud.