[1] _Constitut. Sicil_., i, 3, in Eymeric, _Directorium inquisitorum_, Appendix, p. 14.
Once started on the road to severity, Frederic II did not stop. To aid Gregory IX in suppressing heresy, he enacted at Ravenna, in 1237, an imperial law condemning all heretics to death.[1] The kind of death was not indicated. But every one knew that the common German custom of burning heretics at the stake had now become the law. For by three previous laws, May 14, 1238, June 26, 1238, and February 22, 1239, the emperor had declared that the Sicilian Code and the law of Ravenna were binding upon all his subjects; the law of June 26, 1238, merely promulgated these other laws throughout the kingdom of Arles and Vienne. Henceforth all uncertainty was at an end. The legal punishment for heretics throughout the empire was death at the stake.
[1] _Mon. Germ., Leges_, sect. iv, vol. ii, pp. 196.
Gregory IX did not wait for these laws to be enacted to carry out his intentions.
As early as 1231 he tried to have the cities of Italy and Germany adopt the civil and canonical laws in vogue at Rome against heresy, and he was the first to inaugurate that particular method of prosecution, the permanent tribunal of the Inquisition.
We possess some of the letters which he wrote in June, 1231, urging the bishops and archbishops to further his plans. He did not meet with much success, however, although the Dominicans and the Friars Minor did their best to help him. Still some cities like Milan, Verona, Piacenza and Vercelli adopted the measures of persecution which he proposed. At Milan, Peter of Verona, a Dominican, on September 15, 1233, had the laws of the Pope and the Senator of Rome inscribed in the city's statutes. The _animadversio debita_ was henceforth interpreted to mean the penalty of the stake. "In this year," writes a chronicler of the time, "the people of Milan began to burn heretics." In the month of July, sixty heretics were sent to the stake at Verona. The podestà of Piacenza sent to the Pope the heretics he had arrested. Vercelli, at the instance of the Franciscan, Henry of Milan, incorporated in 1233 into its statutes the law of the Senator of Rome and the imperial law of 1224; it, however, omitted in the last named law the clause which decreed the penalty of cutting out the tongue. In Germany, the Dominican, Conrad of Marburg, was particularly active, in virtue of his commission from Gregory IX. In accordance with the imperial law, we find him sentencing to the stake a great number of heretics.