Employer Demanding NDA After Resignation: How Should I Handle This Threat?

Employer is forcing me to sign a non-disclosure agreement, threatening to file a case against my friends if I don't comply. However, there is no mention in the service agreement that an employee needs to sign such an agreement after resignation. Please advise.

If your friend has already resigned and such resignation has been accepted, then the employer-employee relationship ends there. After cessation of the relationship, the employer cannot ask you to do 'anything'.

On the other hand, you can write to your employer and ask them to stop threatening you and forcing you to sign an NDA since you are no longer in their employment. A copy of such a letter can also be forwarded to the police station as an abundance of caution.