Whether the particular employee is a workman or not, termination without following the principles of natural justice is illegal.
If he is a workman under the ID Act,1947, he can raise a dispute u/s 2-A(1) of the Act before the conciliation officer for the area.
If he happens to belong to supervisory cadre with a salary exceeding Rs.10000/-pm, he can file a civil suit for breach of the contract of employment and claim damages from the management.