Pius XII, 1939-

Surely, there is no one who does not see, if rights are claimed for the state, which is quite absolute and responsible to no one, that this is entirely opposed to naturally ingrained law, and wholly refutes it; and it is clear, likewise, that such rights place at the discretion of rulers of the state the bonds lawfully agreed upon by which nations are joined to one another; and they impede an honest agreement of minds and mutual collaboration for helpful action. If, Venerable Brothers, properly organized and long lasting understandings between states demand this, the bonds of friendship, from which rich fruits arise, demand that peoples recognize the principles and norms of the natural law by which nations are joined to one another, and be obedient to the same. In similar fashion these same principles demand that for every nation its own liberty be preserved, and that those rights be assigned to all by which they may live and may advance day by day on the road of civil progress to more prosperous circumstances; finally, they demand that pacts entered upon, as exacted and sanctioned by international law, remain unimpaired and inviolable.

There is no doubt that then only can nations live peacefully together, then only can they be governed publicly by established bonds, when mutual trust exists between them; when all are convinced that the trust given will be preserved on both sides; finally when all accept these words as certain, “better is wisdom than weapons of war” [cf. Eccles. 9:18]; and, furthermore, when all are prepared to inquire into and discuss a matter more extensively, but not by force and threats to bring about a critical situation, if delays, disputes, difficulties, changes of front stand in the way, all of which indeed can arise not only from bad faith but also from a change of circumstances and from a mutual clash of individual interests.

But then to separate the law of nations from the divine law, so that it depends upon the arbitrary decisions of the rulers of the state as its only foundation, is nothing other than to pull it down from its throne of honor and security, and to hand it over to a zeal which is excessive and concerned with private and public advantage, and which strives for nothing other than to assert its own rights and deny those of others.

2282. Surely, it must be affirmed that in the course of time, because of serious changes in attendant circumstances—which, while the pact was being made, were not foreseen, or perhaps could not even have been foreseen—either entire agreements or certain parts of these sometimes become unjust to either of the stipulating parties, or could seem so, or at least turn out exceedingly severe, or, finally, become such that they cannot be carried out to advantage. If this should happen refuge must necessarily, of course, be taken in a sincere and honest discussion, with a view to making opportune changes in the pact, or to composing an entirely new one. But, on the other hand, to hold proper pacts as fluid and fleeting things,