The Supreme Court on Monday put the brakes on a massive job discrimination lawsuit against mega-retailer Wal-Mart Stores Inc., saying the plaintiffs had not shown justification for sweeping class-action status that could potentially involve hundreds of thousands of current and former female workers.

The ruling — which addressed the claims in the lawsuit only in terms of whether they supported such a huge class action — was a big victory for the nation’s largest private employer and the business community at large.

The high-profile case — perhaps the most closely watched of the high court’s term — is among the most important dealing with corporate employees’ rights that the justices have ever heard, and could eventually affect nearly every private employer, large and small.

“On the facts of the case,” wrote Justice Antonin Scalia for the majority, the plaintiffs had to show “significant proof that Wal-Mart operated under a general policy of discrimination. That is entirely absent here.”

He added, “[In] a company of Wal-Mart’s size and geographical scope, it is quite unbelievable that all managers would exercise their discretion in a common way without some common direction.”

Four more liberal-leaning justices agreed this particular class should not proceed to trial, but criticized the majority for shutting the plaintiffs out “at the starting gate,” to make the claims.

The case is Wal-Mart Stores, Inc. v. Dukes (10-277).