"The death of Frederic II, in 1250, in removing the principal antagonist of the papacy, offered the opportunity of giving practical enforcement to his edicts, and accordingly, May 15, 1252, Innocent IV issued to all the potentates and rulers of Italy his famous bull, Ad extirpanda, a carefully considered and elaborate law which should establish machinery for systematic persecution as an integral part of the social edifice in every city and every state, though the uncertain way in which bishop, inquisitor, and friar are alternately referred to in it shows how indefinite were still their respective relations and duties in the matter. All rulers were ordered in public assembly to put heretics to the ban, as though they were sorcerers. Any one finding a heretic could seize him, and take possession of his goods. Each chief magistrate, within three days after assuming office, was to appoint, on the nomination of his bishop and of two friars of each of the Mendicant Orders, twelve good Catholics with two notaries and two or more servitors whose sole business was to arrest heretics, seize their goods, and deliver them to the bishop or his vicars. Their wages and expenses were to be defrayed by the State, their evidence was receivable without oaths, and no testimony was good against the concurrent statement of any three of them. They held office for six months, to be reappointed or replaced then, or at any time, on demand of the bishop and friars; they were entitled to one third of the proceeds of all fines and confiscations inflicted on heretics; they were exempt from all public duties and services incompatible with their actions. The ruler was bound when required to send his assessor or a knight to aid them, and every inhabitant, when called upon, was obliged to assist them, under a heavy penalty. When the inquisitors visited any portion of the jurisdiction they were accompanied by a deputy of the ruler elected by themselves or by the bishop. In each place visited, this official was to summon under oath three men of good repute, or even the whole vicinage, to reveal any heretics within their knowledge, or the property of such, or of any persons holding secret conventicles or differing in life or manners from the ordinary faithful. The State was bound to arrest all accused, to hold them in prison, to deliver them to the bishop or inquisitor under safe escort, and to execute within fifteen days, in accordance with Frederic's decrees, all judgments pronounced against them. The ruler was further required, when called upon, to inflict torture on those who would not confess and betray all the heretics of their acquaintance. If resistance was made to an arrest, the community where it occurred was liable to an enormous fine unless it delivered up to justice within three days all who were implicated. The ruler was required to have four lists made out of all who were defamed or banned for heresy; this was to be read in public thrice a year and a copy given to the bishop, one to the Dominicans and one to the Franciscans; he was likewise to execute the destruction of houses within ten days of sentence, and the exaction of fines within three months, throwing in prison those who could not pay and keeping them until they should pay. The proceeds of fines, commutations, and confiscations were divided into three parts, one enuring to the city, one to those concerned in the business, and the remainder to the bishop and inquisitors to be expended in persecuting heresy. The enforcement of this stupendous measure was provided for with equally careful elaboration. It was to be inscribed ineffaceably in all the local statute books, together with all subsequent laws which the popes might issue, under penalty of excommunication for recalcitrant officials, and interdict upon the city. Any attempt to alter these laws consigned the offender to perpetual infamy and fine, enforced by the ban. The rulers and their officials were to swear to their observance under pain of loss of office; and any neglect in their enforcement was punishable as perjury with perpetual infamy, a fine of two hundred marks, and suspicion of heresy, involving loss of office and disability for all official position in future.¹"
            Henry Charles Lea, History of Inquisition of Middle Ages vol 1, (1888) [New York: Harbor Press 1955 ] p. 337

Responsibilities of Civil Authorities

            All statues interfering with the free action of the Inquisition were void².

            Similar laws were passed throughout the rest of Europe over the next hundred years, although England managed to avoid passing such laws until the early fifteenth century when statutes against heresy were passed in an attempt to suppress the Lollard movement.

            What else can I add to what Lea already said - magistrates had no real choice but to pass the laws which the Pope directed them to pass and to enforce them as directed by the Pope and his subordinates. If they refused to do as directed, they were tried as heretics and sent to the stake. Eventually, after enough honorable men went to the stake, some one depraved enough or cowardly enough to do the Pope's bidding would fill the magistracy and the Pope's will would be done.

End Notes

1. Lea, History of Inquisition of Middle Ages vol 1, p. 337
   
2. Lea, History of Inquisition of Middle Ages vol 1, p. 341

References

            Henry Charles Lea, History of Inquisition of Middle Ages vol 1, (1888) [New York: Harbor Press 1955 ]