I understand that you are talking about importing requirement,issued by national authority for aging aircraft.Actually,in some contries like India,China and Indonesia,there is limitation for used aircraft in accordance with its age.Aging aircraft is allowed to operated only if it is satisfied many additional maintenance,inspection and record keeping requirements in order to maintain its structure integrity and safe condition.
This information is not confidental but very difficult to find.In my opinion,you can find it in national regulation or ask national authority directly.
If you have something esle or better direction,please share it.
Thanks in advance!