This paper aims to apply the doctrine of siyasah shariyyah to a policy proposal in the area of monetary economics, namely, the Grondona system of conditional currency convertibility, which has been proposed as a practical means of resisting the economic instability caused by the present-day fiat money system. The paper uses library research to review the literature relevant to the Grondona system, and examines the extent to which its operations conform to the principle of siyasah shariyyah, thereby encouraging Maslahah, i.e. the public interest. The paper includes important implications for the policymakers in the Organization of Islamic Cooperation countries for the possible implementation of Grondona system.