The Supreme Court held that asking for union representation during an investigation is a concerted activity. If the employee is fearful, the representative can participate in the investigation and help find out any other information. The Weingarten Rights consist of 3 rules.
The first rule is that the employee must make it clear that he/she wants a union representative with them in the interview before or during the interview. The employer then has three choices. It can allow a union representative to be present and proceed when he/she arrives. It can deny the request and not continue the interview or give the employee the choice of not having the interview without representation or ending the interview.