: “Although it clearly follows from the circumstances that the Pope can err at times, and command things which must not be done, that we are not to be simply obedient to him in all things, that does not show that he must not be obeyed by all when his commands are good. To know in what cases he is to be obeyed and in what not… it is said in the Acts of the Apostles: ‘One ought to obey God rather than man’; therefore, were the Pope to command anything against Holy Scripture, or the articles of faith, or the truth of the Sacraments, or the commands of the natural or divine law, he ought not to be obeyed, but in such commands, to be passed over (despiciendus)…”
"By disobedience, the Pope can separate himself from Christ despite the fact that he is head of the Church, for above all, the unity of the Church is dependent upon its relationship with Christ. The Pope can separate himself from Christ either by disobeying the law of Christ, or by commanding something that is against the divine or natural law. by doing so, the Pope separates himself from the body of the Church because this body is itself linked to Christ by obedience. In this way, the Pope would, without doubt, fall into schism…
"He would do that if he did not observe that which the Universal Church observes in basing herself on the Tradition of the Apostles, or if he did not observe that which has been ordained for the whole world by the universal councils or by the authority of the Apostolic See. Especially is this true with regard to the divine liturgy, as, for example, if he did not wish personally to follow the universal customs and rites of the Church. This same holds true for other aspects of the liturgy in a very general fashion, as would be the case of one unwilling to celebrate with priestly vestments, or in consecrated places, or with candles, or if he refused to make the sign of the cross as other priests do, or other similar things which, in a general way, relate to perpetual usage in conformity with the Canons.
"By thus separating himself apart, and with obstinacy, from the
observance of the universal customs and rites of the Church, the Pope could fall into schism. The conclusion is sound and the premises are not in doubt, since just as the Pope can fall into heresy, so also he can disobey and transgress with obstinacy that which has been established for the common order of the Church. Thus it is that [Pope] Innocent [III] states (De Consuetudine) that it is necessary to obey a Pope in all things as long as he does not himself go against the universal customs of the Church, but should he go against the universal customs of the church, he ought not to be obeyed…" (Summa de Ecclesia [1489])