A judge recently ruled that Walmart must reinstate 16 former employees and give them back pay. These workers were fired after conducting protests during the months of May and June in 2013. In addition to this, the company is required to hold meetings in 29 of its stores informing employees of their right to strike and that they will not be disciplined for it.
See "Labor Judge: Wal-Mart Strikes Protected Under Law", The New York Times, January 22, 2016