The answer to the question posed by Brian Dijkemas title, Is Catholic Social Teaching the Same as Individual Contract Theory? is, I think, obvious: Of course not. Catholic social teaching (CST) and individual contract theory (ICT) are not different names for an identical set of propositions. For example, ICT, at least in its libertarian expression, sees no reason to prohibit exchanges between consenting adults in prostitution, pornography, and drugs. Catholic social teaching unequivocally proscribes such exchanges. I do not see CST as a pale papal Gestetner of Robert Nozick.
Charles W. Baird, "Individualism and Voluntarism," Journal of Markets & Morality 17, no. 2 (Fall 2014): 525-532.