Is it permissible - Policy stating that the employees have to avail earned leave first and followed by other leaves?

Dear All, Is it permissible to make a company policy stating that the employees have to avail earned leave first and followed by other leaves?

How can you evolve such a leave policy?
Earned leave is the leave earned by the employee after putting in, minimum one year of service,
whereas other types of leave could be credited to employees upon their joining duty.
Hence, it is not feasible to evolve such leave policy whereby employees are informed to avail earned leave first and then avail other leaves.

Leave is a benefit of employment to be availed of by the employees according to their necessities or choices subject of course to previous sanction by the employer. Even certain type of leave like sick leave cannot be taken with prior approval. Therefore, it is not within the discretion or administrative power of the employer to prescribe the order,if any to be followed by the employees in the matter of applying for leave.