They were fired for wearing orange shirts to work.  I previously wrote about that here.  Now, they have filed a complaint with the National Labor Relations Board.  See ABA Bar Journal report.  They say they wore the shirts simply to show they were part of the same group when they went out for drinks after work.  But, management thought the orange shirts were some form of protest.  If so, then, yes their actions would be protected by the National Labor Relations Act.  Employees can protest management actions.