I do not know whether this is the right forum to post my problem. I am sorry if my posting is in the wrong forum.

The problem relates to a person X who joins a central government institute while on Lien from a state government. Now this person X while on lien complete his/her 20 years in service in state government while on lien to be eligible for pension under old pension scheme. Then after completion of 20 years X resigns and opts for service in Central Government. Now my questions is :-

1) What are the rules to be eligible for pension(under old pension scheme) while on lien ? Does rule require him to rejoin the state government and then resign ? Otherwise on what basis his resignation is to be considered ?

I would be highly obliged if someone can refer to me the rules/ book from where I can find the solution.