I think the use of the phrase "contractual employee" in your post refers to either a Fixed Term Contract Employee or any contract labor engaged through some external agency. In either case, you cannot have a leave policy exclusively for them vis-a-vis your regular employees. The reason is that the FTC employee is an employee on par with the regular employees but for his fixed tenure, and therefore, he is equally entitled to the benefits of all the conditions of service, including leave. Interestingly, FTC Employees stand to get better in terms of gratuity than the regular Employees of the same establishment by way of gratuity entitlement proportionate to the length of their FTC service consequent on the amendment to the IESO (Central) Rules in 2018. In the case of contract labor, whatever labor law pertaining to conditions of employment applicable to the Principal Employer's establishment would be applicable without any modifications.