hi sunil
i dont think there is any labour law for the probation period. Normally it will the policy for the company to keep employee on probation for a period of time , say 6 months or 1 year. but do not keep an employee on probation or as a trainee for more than 240 working days. please refer to an act called conferment of permanent status act, wherein it says that an employee should be made permanent or deemed as a permanent employee once he or she had worked for 240 days in a year. as far as the probationary and trainee period you may include as a condition in your company HR policy like one year, 6 months etc.,
any further doubt you can ask me
regards
R Devarajan