The National Labor Relations Board has ruled that employers cannot stop workers from filing group or class actions that are work related. Many companies have employees sign agreements that they will pursue any claims individually through arbitration. The ruling applies to both union and nonunion workers. There are expected to be challenges to the ruling, and opponents say that the NLRB has overstepped its purposes, and that a Supreme Court ruling regarding arbitration agreements covers class actions.
See "Labor Board Backs Workers on Joint Arbitration Cases", Steven Greenhouse, The New York Times, January 8, 2012