When is it permissible for the one who enforces good (al-Muhtasib) to publicly expose a person who commits a reprehensible act (al-Munkar)?

The one who commits an evil act should be denounced, but his sin should be concealed and not publicized if he is not openly defiant in his wrongdoing. This is in emulation of the story of Ma'iz, when the Prophet, peace and blessings be upon him, said to Hazzal: "If only you had covered him with your garment, it would have been better for you." As for the one who openly commits sins, it is permissible to publicize his affair and expose him, so that he and others may be deterred.