Par. 1930 of the Catechism says rights “are the basis of the moral legitimacy of every authority.” It doesn’t say rights are “necessary for” legitimacy, it says they are “the basis of” legitimacy. The formulation echoes the statement in the Declaration of Independence that governments are instituted to secure rights. It seems to suggest that the Church agrees with the Declaration of Independence on the point.
The formulation would be more comprehensible if the Catechism defined “rights,” which it doesn’t. It appears that the Church has never said in any clear way just what it means by “rights.” As used by other people, the word usually has to do with rights to something one actually desires. That’s not enough to justify what the Catechism says. Participation in society is part of what makes us what we are, so it’s part of what forms our desires. If “rights” is used in its usual meaning, it has nothing to say about what kind of desires society forms in us, and so can’t possibly be the measure of the legitimacy of institutions.
To an extent it is through society that we come to understand the good, beautiful and true and participate in them. That’s obviously true of the society that we call the Church, but it’s also true of other societies. So it seems that the legitimacy of social authorities should depend not only on whether they enable us to do and get what we choose, but also on what things they present to us and foster as good.
One could, of course, speak of a right to a social order that is ordered toward the good, beautiful and true, that leads people to desire a good life and facilitates their living it. No-one speaks that way, though. So if the Church is going to use the language of rights it seems to me they should make it clear to everyone just what they mean by it. Because what is the advantage of saying things that sound good to people and will go down easy if they don’t convey what’s intended?