I found a nice discussion of the National Labor Relations Act and Non-Union Employees at this site:  http://www.fredlaw.com/articles/employment/empl_0305_tbk.html

It talks about the extension of the Weingarten Rights to non-union employees.  This was a topic that came up on this board over the weekend.  It makes some important distinctions about who can be present and under what circumstances someone can be present.

"Weingarten Rights do not apply to a meeting to inform an employee of disciplinary action (as opposed to an interview to investigate whether disciplinary action is appropriate).  In addition, the employee who invokes Weingarten rights has a right to have a co-worker present for the interview; Weingarten does not afford the right to have a supervisor or manager, or an attorney or any other non-employee, present."