After the firing of Arthur T. Demoulas last month, hundreds of Market Basket employees walked off the job. On August 20th an employee filed a charge against the company citing an unsafe and hostile workplace environment. If there is imminent threat to employees, the NLRB could seek an injunction against the company, however that seems unlikely in this circumstance according to an observer.
See "Market Basket Worker Files Complaint with Labor Board", Jack Newsham, The Boston Globe, August 25, 2014