"It could be detrimental to any corporation subject to any case that may involve claims that can be assembled into a class," he said. "This would lower the bar on what constitutes a class."

Wal-Mart is appealing the case, Dukes, et al. v. Wal-Mart Stores, Inc. The U.S. Court of Appeals for the Ninth Circuit in San Francisco--considered the epicenter of class-actions--ruled in April by a 6-5 vote that the class action could go forward. That ruling upheld a decision by the District Court for the Northern District of California to certify class-action status because the women were united by their allegations of discrimination.

Mr. Maatman said the Supreme Court decision will be "transformational" in the standards for class action certification, and will provide a roadmap going forward. Currently, the map given by the Ninth Circuit to plaintiffs' attorneys guides them to "file colossal employment class-actions."

"This is the big one that will set the standards for all other class actions," Mr. Maatman said. Ultimately the ruling will tell employers and carriers what they will need to do to "batten down the hatches," he added.

Arguments in the case will begin in the spring, with a ruling likely by June 2011.

Wal-Mart said in a statement that "confusion in class action law is harmful to everyone." The issues "reach far beyond this particular case," said the retailer, which has argued that the thousands of women do not have enough in common to warrant class-action status. They worked at 3,400 stores in 170 job classifications for different managers, and were paid differently, according to court records.

Kenneth Ross, of the Claims and Legal Group at Willis, said that if these plaintiffs can be considered a class, "you're going to open a Pandora's Box for plaintiffs' attorneys to find other cases - be it environmental, securities or any other type of area - that may have not been ripe for this type of case before."

"It will be a while different story if class status is upheld," he added.