A federal appeals court is set soon to consider when companies can literally draw a line marking where striking workers are allowed to protest, in a dispute sparked by a labor board ruling against a Walmart store in California.

The U.S. Court of Appeals for the Ninth Circuit will consider the case OUR Walmart v. National Labor Relations Board on April 11. The case, closely watched by the business community, confronts the test used to determine when a protest held inside a store is protected by federal labor law.

The Obama-era labor board in 2016 ruled for a group of employees who were fired after staging a demonstration within a Walmart. A coalition of major business groups, including the U.S. Chamber of Commerce, the American Hotel and Lodging Association and the National Retail Federation, are backing Walmart in the appeal. The groups, in an amicus brief filed by Morgan, Lewis & Bockius, called the NLRB decision a “dangerous precedent that seriously upsets” labor law.

“Although employees have the right to strike, picket, and engage in demonstrations in a labor dispute, employers have the right to use their property to conduct their business and, in a retail environment, to serve their customers,” the Morgan Lewis team, including appellate veteran Allyson Ho, said in the brief. “Federal labor law strikes a fair, sensible balance by precluding in-store demonstrations that prevent the employer from conducting business and serving its customers.”

The case is rooted in a worker-led protest at a Walmart store in Richmond, California. Complaining about work conditions, the employees held banners and stood in protest inside the store. Six employees, who joined dozens of contract workers, were ultimately terminated for their participation in the work stoppage.

The workers alleged the Richmond store unlawfully restricted employees from wearing union insignia at work and that abusive and anti-union comments were made toward employees and contractors. The workers held the protest on the same day Walmart was celebrating a grand reopening. The protest included a banner in an area near customer service.

Then-NLRB chairman Mark Gaston Pearce and fellow Democratic member Kent Hirozawa said the in-store protest activity was protected under the National Labor Relations Act.

Republican member Philip Miscimarra, who has since rejoined Morgan Lewis, dissented. He drew a distinction between work stoppages in the retail environment, where customers are present, and those in factory or other workplaces where they are not. The applicable balancing test, Miscimarra argued, does not apply in the retail context, where a worker protest can be a disruption to customers.

Attorneys for the board told the Ninth Circuit in July that labor law has long protected the rights of employees to “pressure their employer by remaining in their workplace for a reasonable period of time during a work stoppage.” The board uses a 10-factor test to establish what is a “reasonable period of time.” Those factors include: whether the protest was peaceful; the duration of the stoppage; and whether workers tried to seize property.

“The employees did not seize Walmart's property, and Walmart's hypothetical constitutional theory—which it concedes would only apply if a seizure had occurred—is speculative at best and otherwise mistaken,” the NLRB said in its appeals court brief.

The business groups counter that the consequences of the board's decision will “lead to absurd results to the detriment of businesses and customers alike.” Their brief raised a series of hypothetical scenarios that could result if the Ninth Circuit upholds the labor board's finding against Walmart.

“Will restaurant workers be permitted to picket around customers' tables while they are eating their meals? Will hotel workers be permitted to march through the halls of a hotel, chanting with bullhorns and waking guests in their rooms? Will retail workers be permitted to demonstrate in the aisles as customers are shopping? Will television workers be permitted to demonstrate behind anchors during a live broadcast of the nightly news?”

The business groups said the 10-factor test has become “untethered” from basic principles of labor law.

“It is entirely unreasonable to expect the manager on duty even to know—much less to correctly apply—the ten factors that the NLRB apparently expects to be considered and balanced in the heat of the moment,” the lawyers for the business groups wrote. “Even if the manager has a labor lawyer on speed dial, it will be difficult to predict what conclusion the NLRB will reach months or years after the fact.”

The Organization United for Respect at Walmart, is represented by David Rosenfeld at Weinberg, Roger & Rosenfeld. Walmart is represented by a team from Steptoe & Johnson LLP.