Dear Uzma,
There is a lot of difference between an "unlawful activity" and "getting into or participating as a union member."
You can terminate services of an employee for his participation in any unlawful activities, as prescribed under the laws of the country, or international laws, but his becoming a member and participating in a lawfully formed union is not an unlawful activity.
If you are representing an organization within India, restricting any staff member to associate in any union or association would mean an unconstitutional act on the part of the organization, as you and your organization would be violating the fundamental rights of the employees, as citizens of India, as these fundamental rights are considered to be the base of the Constitution of India.
So, no doubt, you can include the clause of termination on account of unlawful activity, BUT NOT for becoming a member of a lawfully formed union or association. However, you can include the clause of termination on account of becoming a member or participating in an organization banned by the Government of India.
PS Dhingra
Vigilance & Transformation Management Consultant
Dhingra Group of management & Educational Consultants
New Delhi