bridler

Someone or something that bridles (puts a bridle on).

Someone or something that restrains and governs, like with a bridle.

The Prelats which boaſt themſelves the only bridlers of Schiſm, God knows have been ſo cold and backward both there and with us to repreſs Hereſie and idolatry, that either through their careleſſneſs or their craft all this miſchief is befaln.