In his 1234 Decretals, Pope Gregory IX invested the doctrine of perpetua servitus iudaeorum – perpetual servitude of the Jews – with the force of canonical law. Pope Gregory was a principal figure in the institutionalization of Church teaching that discriminated against Jews, and condemned them to an inferior status in Christendom.
"According to this, [the 1234 Decretals] Jews would have to remain in a condition of political servitude and abject humiliation until Judgment Day. The doctrine then found its way into the doctrine of servitus camerae imperialis, or servitude immediately subject to the Emperor's authority, promulgated by Frederick II. The second-class status of Jews thereby established would last until well into the 19th century" (quoted from the Wikipedia article on Pope Gregory IX, accessed 11-25-2008. The Wikipedia article cites a specific reference for the information.)