This decree was proclaimed during Session 5 of the Council of Constance, on April 6, 1415. The decree is generally mentioned as being in direct contradiction with the First Vatican Council on papal infallibility (Pastor Aeternus). But how can it? Haec Sancta precedes Pastor Aeternus by more than 400 years! To be faithful to history we need to assert that it is Pastor Aeternus that contradicts Haec Sancta. In other words, Pius IX went directly against the established edicts of the Church, and should have been deposed, censured, and released to civil authorities for crimes committed (he had a number of his opponents put to death). Alas, he was the Pope during the era of despotism in the late 19th Century Europe, and got away with it all.
Here is the English translation of the entire text of Haec Sancta:
In the name of the holy and undivided Trinity, Father and Son and holy Spirit. Amen. This holy synod of Constance, which is a general council, for the eradication of the present schism and for bringing unity and reform to God's church in head and members, legitimately assembled in the holy Spirit to the praise of almighty God, ordains, defines, decrees, discerns and declares as follows, in order that this union and reform of God's church may be obtained the more easily, securely, fruitfully and freely.
First it declares that, legitimately assembled in the holy Spirit, constituting a general council and representing the catholic church militant, it has power immediately from Christ; and that everyone of whatever state or dignity, even papal, is bound to obey it in those matters which pertain to the faith, the eradication of the said schism and the general reform of the said church of God in head and members.
Next, it declares that anyone of whatever condition, state or dignity, even papal, who contumaciously refuses to obey the past or future mandates, statutes, ordinances or precepts of this sacred council or of any other legitimately assembled general council, regarding the aforesaid things or matters pertaining to them, shall be subjected to well-deserved penance, unless he repents, and shall be duly punished, even by having recourse, if necessary, to other supports of the law.
Next, the said holy synod defines and ordains that the lord pope John XXIII may not move or transfer the Roman curia and its public offices, or its or their officials, from the city of Constance to another place, nor directly or indirectly compel the said officials to follow him, without the deliberation and consent of the same holy synod. If he has acted to the contrary in the past, or shall in the future, or if he has in the past, is now or shall in the future fulminate any processes or mandates or ecclesiastical censures or any other penalties, against the said officials or any other adherents of this sacred council, to the effect that they should follow him, then all is null and void and in no way are the said processes, censures and penalties to be obeyed, inasmuch as they are null and void. The said officials are rather to exercise their offices in the said city of Constance, and to carry them out freely as before, as long as this holy synod is being held in the said City.
Next, that all translations of prelates, or depositions of the same, or of any other beneficed persons, officials and administrators, revocations of commendams and gifts, admonitions, ecclesiastical censures, processes, sentences and whatever has been or will be done or accomplished by the aforesaid lord pope John or his officials or commissaries, since the beginning of this council, to the injury of the said council or its adherents, against the supporters or participants of this sacred council, or to the prejudice of them or of any one of them, in whatever way they may have been or shall be made or done, against the will of the persons concerned, are by this very fact, on the authority of this sacred council, null, quashed, invalid and void, and of no effect or moment, and the council by its authority quashes, invalidates and annuls them.
Next, it declares that the lord pope John XXIII and all the prelates and other persons summoned to this sacred council, and other participants in the same synod, have enjoyed and do now enjoy full freedom, as has been apparent in the said sacred council, and the opposite has not been brought to the notice of the said summoned persons or of the said council. The said sacred council testifies to this before God and people.