Hi Kumaracme,
A writ? We assume the employee has not yet resigned. Generally a write is filed when one's fundamental rights are violated, and it can be of civil or criminal nature.
It would be more helpful if you share more details and the context of the issue, but you yourself can also see why the said employee filed a writ petition, and in which court they did so.
Also, please check what you had given to them in writing about their letter of appointment and job description. If these documents mentioned the transferability of the job, and if the employee agreed, then you have a signed contract, and there is no ground for the writ (again, we are assuming a lot here, more information would be helpful).
Further, what are your service rules under the the Industrial Employment (Standing Orders) Act, 1946? do you have your own service rules, or have you adopted the model rules? If those rules state the transferability of the job and if the procedure for raising grievance has been elaborated there, then the employee should have resorted to that first.
In case if you do not have legal background, it would be better to seek counsel.
Hope this helps.
Best wishes,
Team HRM For Non-HR Managers