Serious suggestions have been made to us that communities in certain places, to the divine displeasure and injury of the neighbour, in violation of both divine and human law, approve of usury. By their statutes, sometimes confirmed by oath, they not only grant that usury may be demanded and paid, but deliberately compel debtors to pay it. By these statutes they impose heavy burdens on those claiming the return of usurious payments, employing also various pretexts and ingenious frauds to hinder the return. We, therefore, wishing to get rid of these pernicious practices, decree with the approval of the sacred council that all the magistrates, captains, rulers, consuls, judges, counsellors or any other officials of these communities who presume in the future to make, write or dictate such statutes, or knowingly decide that usury be paid or, if paid, that it be not fully and freely restored when claimed, incur the sentence of excommunication. They shall also incur the same sentence unless within three months they delete from the books of their communities, if they have the power, statutes of this kind hitherto published, or if they presume to observe in any way these statutes or customs. Furthermore, since money-lenders for the most part enter into usurious contracts so frequently with secrecy and guile that they can be convicted only with difficulty, we decree that they be compelled by ecclesiastical censure to open their account books, when there is question of usury. If indeed someone has fallen into the error of presuming to affirm pertinaciously that the practice of usury is not sinful, we decree that he is to be punished as a heretic; and we strictly enjoin on local ordinaries and inquisitors of heresy to proceed against those they find suspect of such error as they would against those suspected of heresy.
Constitution 29, Council of Vienne, A.D. 1312.