Unam sanctam
The Bull also states, "We are informed by the texts of the gospels that in this Church and in its power are two swords; namely, the spiritual and the temporal."[12] The swords being referred to are a customary reference to the swords yielded by the Apostles upon Christ's arrest (Luke 22:38; Matthew 26:52).[2] Early theologians believed that if there are two swords, one must be subordinate to the other. This then became a spiritual hierarchal ladder, the spiritual judges the secular "on account of its greatness and sublimity,[2] while the lower spiritual power is judged by the higher spiritual power, etc.[11] Thus, it was concluded, the temporal authorities must submit to the spiritual authorities, not merely on matters concerning doctrine and morality: "For with truth as our witness, it belongs to spiritual power to establish the terrestrial power and to pass judgment if it has not been good." The bull ends, "Furthermore, we declare, we proclaim, we define that it is absolutely necessary for salvation that every human creature be subject to the Roman Pontiff."[12]
https://en.wikipedia.org/wiki/Unam_sanctam
It was a rebuke of a rebellious monarch, King Philip the Fair of France, who claimed to be a Catholic but was more-or-less trying to take over the Church in France. It was not a general treatise on whether or not non-Catholics can be saved, and in fact quotes work of St Thomas Aquinas where he explains exactly how and under what conditions persons outside the visible Church can be saved.