From Halopedia, the Halo wiki
A regional commandant was a Forerunner official charged with the administration of a given area of the ecumene. A regional commandant had the authority to appoint privateers by issuing letters of marque. During his exile after the Battle of the Capital, Faber, the Master Builder, carried out his own small-scale operation to seize Flood-controlled vessels in a fringe region of the ecumene under the letter of marque of the local regional commandant.
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