Unsheduled Leave ANd Habit of regularizing leave only after reminder

One of the officer working under me , is in the habit of not delivering his duties properly and on frequent unsheduled leaves quoting various personal and health reasons.
On return from leave the officer does not submit leave application and joining report for several occasions may be around 10 leaves.The leaves application were pending for nearly three monhts.Only after reminder after three months the officer submits his leave application.
The officer had a similar warning from Adminstration in the previous year for non regularization of leave after joining duty.
I am Divisional Head and informed to the adminstrative officer.
The Adminstrative officer has informed to issue a memo.
I am in Central Govt. Hence to avoid any type of retaliation legally by the officer for mistakes any in the memo to be issued. I wanted your guidance on issuing a memo under such situation.

Leave is not a matter of right but is subject to exigencies of service. If somebody is very lax in applying for leave then a memo could be issued and it needs to be stressed that in spite of directions many times in the past it is still seen that leave application is never submitted in time. Indeed leave could be refused and the individual could be marked absent for such absence which would remain unauthorised. It is necessary to take action in such cases, lest others follow the wrong example.

Our Office follow CCS Rules being Central Govt.
If leave is rejected informing the officer's delay in submission does the officer have any room to confront or challenge legally.
On what Rule of CCS can we reject such leave to make it unauthorized absence.

Rule 7 of CCS Leave Rules reads as follows :
7. Right to leave
(1) Leave cannot be claimed as of right.
(2) When the exigencies of public service so require, leave of any kind may be refused or revoked by the authority competent to grant it, but it shall not be open to that authority to alter the kind of leave due and applied for except at the written request of the Government servant.
Using these powers the leave requested could be refused. once leave is refused, the absence becomes unauthorised.
The aggrieved employee could take up his grievance but it could be effectively replied stating the habit of not timely applying for leave and relying on Rule 7. The legal position is very clear that leave cannot be claimed as a matter of right and exigencies of service is the prime consideration in granting/non-grant of leave. Habitual abrupt absence and non-submission of application even after reminder amounts to dereliction of duty and insubordination

The contents of the posting suggest that you are scared of this particular employee even though he has been indulging in willful mischief. Why? If the employee has not regularised his absence by applying for leave, as admissible, he is not entitled for the pay for the days/period he has remained absent. Onus rests with him applying for leave, that too, in advance except in the case of casual leave. If he has not applied for leave, no pay need to be paid for the periods of absence.