But she also seemed concerned about how such a sprawling case could be managed by a judge if the women were allowed to proceed as a class. She asked Sellers how a judge could deal with an issue such as claims for back pay.
"But what seems to me is a very serious problem in this case is: How do you work out the back pay?" she asked.
Professor Suzette Malveaux of the Catholic University in Washington, D.C., who signed an amicus brief on behalf of the women plaintiffs, said that the size of the class will pose challenges if it is allowed to go forward.
"But this case is like many other employment discrimination class actions," she said. "While it gets a lot of attention for the number of employees, that is what the company asked for.
"If you are going to employ so many employees and be a worldwide player, than you assume the risk that you might be liable for billions of dollars of back pay. It's a function of the size of the company, it shouldn't immunize them from the law simply because they are big."
Outside court today, Betty Dukes, one of the original plaintiffs who works as a greeter at Walmart, agreed.
"Walmart may be a big company, " she said, "but they're not big enough where they can't be challenged in a court of law. If you do wrong, then you should be held accountable, from the least of us to the greatest of us."