Once the shares are transmitted to the NRI account (Non-PINS-Non-repatriable) of the legal heir, he can liquidate these shares in the secondary market without PINS/ RBI permission. PINS approval is not required for selling inherited shares. PINS approval will be required only for transaction in secondary market.
(The guidelines in FEMA states that NRI can hold, own, transfer security, if such security was acquired , held or owned by such person when he was resident in India or inherited from a person who was resident in India. Therefore NRI does not require RBI permission to hold and transfer of shares , acquired by inheritance through transmission of shares.)