instantly how we are to interpret the
_animadversio debita_ of contemporary documents.

Frederic II exercised an undeniable influence over Gregory IX, and
the Pope in turn influenced the emperor. Gregory wrote denouncing the
many heretics who swarmed throughout the kingdom of Sicily (the two
Sicilies), especially in Naples and Aversa, urging him to prosecute
them with vigor. Frederic obeyed. He was then preparing his Sicilian
Code, which appeared at Amalfi in August, 1231. The first law,
_Inconsutilem tunicam_, was against heretics. The emperor did not
have to consult any one about the penalty to be decreed against
heresy; he had merely to copy his own law, enacted in Lombardy in
1224. This new law declared heresy a crime against society on a par
with treason, and liable to the same penalty. And that the law might
not be a dead letter for lack of accusers, the state officials were
commanded to prosecute it just as they would any other crime. This
was in reality the beginning of the Inquisition. All suspects were to
be tried by an ecclesiastical tribunal, and if, being declared
guilty, they refuse to abjure, they were to be burned in the presence
of the people.[1]

[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 wrot