Continued from page 1

“Some employers will react to that by banning all types of solicitations, because they don’t want to allow the unions access to their property,” he said.

The case also could overturn a precedent on workplace email policies. In 2007, the NLRB found that the Register-Guard, a daily newspaper in Eugene, Ore., was within its rights to prevent employees from sending union-related emails, while allowing them to send other personal emails. But the Roundy's case might call into question that kind of distinction.

“The concern is the board will use Roundy's as a vehicle to reverse [the Register-Guard] decision,” Mr. Lotito said. “If the board uses this for broader email restrictions, then, obviously, the case takes on tremendous significance.”

Ronald Meisburg, a partner at New York-based Proskauer Rose LLP and a former board member and general counsel at the NLRB, said such an outcome is possible, given how the board has approached the case.

“Based on the board’s invitation to file briefs, it seems at least possible that the board will use Roundy's to bring the Register-Guard test more in line with stricter test of Sandusky Mall,” he said.

That could mean companies will face a choice of either banning all personal email or allowing union-related email.

“As a practical matter, if Register-Guard is reversed, it means that company email systems are going to be utilized by employees to promote unions, because there is no employer that has the stomach, time or capability to monitor and prohibit all of these communications that take place on the company email system and have nothing to do with work,” Mr. Lotito said.

Roundy's has declined to comment on the case.