29 CFR 785.28 - Involuntary attendance.
Attendance is not voluntary, of course, if it is required by the employer. It is not voluntary in fact if the employee is given to understand or led to believe that his present working conditions or the continuance of his employment would be adversely affected by nonattendance.
Title 29 published on 2013-07-01
no entries appear in the Federal Register after this date.