“Though lying is forbidden, we may be allowed to conceal the truth, or to disguise it under ambiguous or equivocal words or signs, for a just cause, and when there is no necessity to confess the truth. If by that means one can rid himself of dangerous pursuits, he is permitted to use it; for in general it is not true to say that, when interrogated by public authority about his faith, he is obliged to reveal it. When you are not questioned as to your faith, you are not only allowed to conceal it, but it is often more to the glory of God and the interest of your neighbor. If, for example, you are among a heretical people, you can do more good by concealing your faith; or if, by declaring it, you are to cause great trouble or death. It is temerity to expose one’s life.” (Liguori, L. 2.)
The Pope has the right to release from all oaths.
“As for an oath made for a good and legitimate object, it seems that there should be no power capable of annulling it. However, when it is for the good of the public, a matter which comes under the immediate jurisdiction of the Pope, who has the supreme power over the Church, the Pope has full power to release from that oath.” (St. Thomas, Quest. 89, art. 9, vol. iv.)
The Roman Catholics have not only the right, but it is their duty to kill heretics.
“Excommunicatus privatur omni alia civili communicatione fidelium, ita ut ipsi non possit cum aliis, et si non sit toleratus, etiam aliis cum ipso non possit communicare; idque in casibus hoc versu comprehensis. Os, orare, cammunio, mensa negatur.”
Translated: “Any man excommunicated is deprived of all civil communication with the faithful, in such a way that if he is not tolerated they can have no communication with him, as it is in the following verse: ‘It is forbidden to kiss him, pray with him, salute him, to eat or to do any business with him.’” (St. Liguori, vol. ix., page 62.)
“Quanquam heretici tolerandi non sunt ipso illorum demerito, usque tamen ad secundam correptionem expectandi sunt, ut ad sanam redeant ecclesiæ fidem; qui vero post secundam correptionem in suo errore obstinati permanent, non modo excommunicationis sententia sed, etiam sæcularibus principibus exterminandi tradendi sunt.”
Translated: “Though heretics must not be tolerated because they deserve it, we must bear with them till, by a second admonition they may be brought back to the faith of the Church. But those who, after a second admonition, remain obstinate in their errors, must not only be excommunicated, but they must be delivered to the secular powers to be exterminated.”
“Quanquam heretici revertentes, semper recipiendi sint ad pœnitentiam quoties cumque relapsi fuerint; non tamen semper sunt recipiendi et restituendi ad bonorum hujus vitæ participationem ... recipiumtur ad pœnitentiam ... non tamen ut liberentur a sententia mortis.”
Translated: “Though the heretics who repent must always be accepted to penance, as often as they have fallen, they must not in consequence of that always be permitted to enjoy the benefits of this life. When they fall again they are admitted to repent. But the sentence of death must not be removed.” (St. Thomas, vol. iv., page 91.)