The U.S. Supreme Court suggested it may shield Wal-Mart Stores Inc. from a gender-bias suit on behalf of potentially 1 million female workers, in a case that may mean tighter restrictions on class action suits, Bloomberg reported.

Hearing arguments Tuesday in Washington, D.C., the justices gave a generally receptive audience to the world’s largest employer, which argued that claims by workers around the country are too varied to proceed as a single lawsuit. The class action, approved by a federal appeals court, would be the largest-ever job-bias case against a private employer.

Tuesday’s arguments suggested the court might divide roughly along gender lines itself, with the three female justices — Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan —  emerging as perhaps the strongest supporters of the class action. Justices Antonin Scalia, Anthony Kennedy and Samuel Alito voiced skepticism.

The case marks the court’s first look in a dozen years at the standards for certifying a class action. Worker advocates say a victory for Wal-Mart, based in Bentonville, Ark., would crush efforts to force change at companies steeped in bias. Corporate groups say a ruling allowing the suit might unleash a wave of employment, antitrust and product-liability suits.

The case threatens Wal-Mart with billions of dollars in damages. Filed in 2001, the suit aims to cover every woman who worked at the retailer’s Wal-Mart and Sam’s Club’s stores at any point since December 1998.

More than 100 Wal-Mart employees have filed sworn statements saying they were paid less and given fewer opportunities for promotion than male colleagues.