Dear Peripa Saikrishna,
Generally, employers reserve the right to transfer an employee from one department to another. A clause with this effect is inserted in the appointment letter.
The employee is employed in the organisation. The employment is not specific to the department unless it is specifically mentioned in the appointment letter.
When the notice for inter-department transfer is issued, it is mentioned whether the transfer is for "a specific period" or "till further order" or "permanently".
As far employee is concerned, after working for a certain period in the transferred department, he/she may seek to go back to the original department. The employee may put up an application to this effect but whether to accede to the request of the employee or not is the prerogative of the authorities concerned.
Thanks,
Dinesh Divekar