Notice Period ti meant to search for replacement and also to ensure that the outgoing employee reasonably complete pending jos.
Letters do not say that Notice need to be given for 30 working days. Generally notice period mentions the numbber of days or number of months. There is generally no mention about working days,
Hence refusal to sanction leave is not legally correct. ut other rules pertaining to leave should bbe followed. Sanctioning leave is always at the discretion of the manager. He can not reject leave stating that you are on Notice period. he can always say that since you need to complete the job, leave is not sanctioned.
Legally rejection based on Notice period is not correct.
However, rules pertaining to sanction of leave in general can e imposed
T Sivasankaran