Is a treaty of dhimma or truce valid if concluded by someone other than the Imam or his deputy?

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A treaty of dhimma (protection for non-Muslims living under Muslim rule) or a truce is only valid if concluded by the Imam (ruler) or his deputy. This position is held by Al-Shafi'i, and no disagreement is known regarding this matter. The validity stems from the fact that such matters pertain to the Imam's discretion and judgment regarding public interest. Furthermore, the treaty of dhimma is considered a perpetual contract, meaning no one else may preempt the authority of the Imam in concluding it.