NOC to Librarian for 13th RLST

One of my friends has joined as a Librarian just two and a half years ago in a Govt. Aided High School. Now he wants to apply for the 13th RLST for post of an Asst. Teacher in H/PG category. But his HM is not ready to issue him NOC saying that he will have to complete 3 years of service in his present post before getting NOC. Now he needs a circular/ GO/ or any other document which may assist him convincing his HM that he is eligible to have NOC for applying for a better post right now. Any kind of help regarding the above from any of my learned mates here would be highly appreciated. Thank you.