Who is responsible for distributing the fifth share in the current era?

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The sending of the Imam's governors and collectors is impossible in the current time because the Imam no longer holds authority except in few Muslim lands, nor does he have jurisdiction or command regarding military campaigns (Ghazw). Furthermore, since this is one of the shares of the Khums, its universal distribution is not obligatory, just like the distribution of its other shares. Therefore, every reigning Sultan should distribute it within the limits of what is possible in his own territories.