Paul IV sought to strictly enforce earlier canonical restrictions against the Jews — as those prohibiting their practising medicine among Christians, employing Christian servants, and the like — but he also restricted them in their commercial activity, forbade them to have more than one synagogue in any city, enforced the wearing of the yellow hat, refused to permit a Jew to be addressed as "signor", and finally decreed that they should live in a designated area separated from Christians. The last measure was carried out in Rome with unrelenting cruelty.