Scenirio human resource case | Human Resource Management homework help

Tasha was using the computer inappropriately on 2/21/2017 between the hours 4:58 pm -8:02pm.  Tasha was using yahoo instant messenger and watching TV shows, during work hours.  Tasha was called into the Managers office to be addressed, and owned up and was told there was nothing to sign right now but it’s at Human Resource for review.  Tasha was later called back to manager office to sign the written warning that was decided based on the amount of misuse she was doing.   Tasha also asked if this writ up carried an expiration date and manager left to asked HR and the answer was no and that if a promotion or activity like Work Trip  would come up they would not hold it against Tasha, forever and it was going to be based off work performance.  Later Tasha was then called in later to get told they revoked the invitation to (incentive work trip). 

*Nowhere in the email is invite there a disclaimer stating the invite was contingent or can be revoked at any time.

*Her team signed a huddle attendance sheet when manager went over the policy about computer are being monitor and about policy but they use her signature on the write up of receipt and review of employee handbook when Tasha was hired on 05/09/2013. 

*A colleague also broke the same rule by sending a message through skype that was not work related but gave a verbal warning. 

Where any labor or EEOC Laws broken?  If so proof of the laws if any was broken.

If Tasha was to fight her case how can she win based off the law and what is it she needs to do to help win this case.