Shulchan Arukh, Orach Chayim 148/שולחן ערוך·אורח חיים קמ״ח

1That the Prayer Leader May Not Uncover the Ark. Containing 1 S'if:The prayer leader does not have permission to uncover the Ark in [front of] the community - as long as they are in the synagogue. (Rashi explains that they were accustomed to bring the Torah scroll from another house where it was kept safe etc. and it was a burden on the congregation to have to wait there. See further inside in Orach Chaim)