This section of Gaudium et Spes addresses property rights, starting on a sensible point:
Since property and other forms of private ownership of external goods contribute to the expression of the personality, and since, moreover, they furnish one an occasion to exercise his (or her) function in society and in the economy, it is very important that the access of both individuals and communities to some ownership of external goods be fostered.
Ownership is not just a legal and moral right, but it also presumes a responsibility:
Private property or some ownership of external goods confers on everyone a sphere wholly necessary for the autonomy of the person and the family, and it should be regarded as an extension of human freedom. Lastly, since it adds incentives for carrying on one’s function and charge, it constitutes one of the conditions for civil liberties.(Cf. Leo XIII, encyclical letter Rerum Novarum: AAS 23 (1890-91) pp. 643-646, Pius XI, encyclical letter Quadragesimo Anno: AAS 23 (1931) p. 191; Pius XII, radio message of June 1, 1941: AAS 33 (1941), p. 199; Pius XII, radio message on Christmas Eve 1942: AAS 35 (1943), p. 17; Pius XII, radio message of Sept. 1, 1944: AAS 36 (1944) p. 253; John XXIII, encyclical letter Mater et Magistra: AAS 53 (1961) pp. 428-429.)
Despite modern legalities, and the recognition of non-physical realities as property, the same moral structure of rights and duties applies:
The forms of such ownership or property are varied today and are becoming increasingly diversified. They all remain, however, a cause of security not to be underestimated, in spite of social funds, rights, and services provided by society. This is true not only of material property but also of immaterial things such as professional capacities.
A slightly more explicit rendering of the importance of the common good:
The right of private ownership, however, is not opposed to the right inherent in various forms of public property. Goods can be transferred to the public domain only by the competent authority, according to the demands and within the limits of the common good, and with fair compensation. Furthermore, it is the right of public authority to prevent anyone from abusing his private property to the detriment of the common good.(Cf. Pius XI, encyclical letter Quadragesimo Anno: AAS 23 (1931) p. 214; John XXIII, encyclical letter Mater et Magistra: AAS 53 (1961), p. 429.)
And more on community considerations:
By its very nature private property has a social quality which is based on the law of the common destination of earthly goods.(Cf. Pius XII, radio message of Pentecost 1941: AAS 44 (1941) p. 199, John XXIII, encyclical letter Mater et Magistra: AAS 53 (1961) p. 430.) If this social quality is overlooked, property often becomes an occasion of passionate desires for wealth and serious disturbances, so that a pretext is given to the attackers for calling the right itself into question.
I’m thinking of my experiences in American suburbia. I let one thistle grow in my Chicagoland backyard once, and my next door neighbor complained: even “one weed” was offensive. My housemate planted a small US flag next to the walk on Memorial Day. He left it out Tuesday and that evening we found it in our mailbox. And that was during Gulf War I, mind you. The American take on this portion would be mainly on property (such as real estate) that affects the economic value of other people’s property. The council bishops, naturally, are more concerned about the exploitation angle:
In many underdeveloped regions there are large or even extensive rural estates which are only slightly cultivated or lie completely idle for the sake of profit, while the majority of the people either are without land or have only very small fields, and, on the other hand, it is evidently urgent to increase the productivity of the fields. Not infrequently those who are hired to work for the landowners or who till a portion of the land as tenants receive a wage or income unworthy of a human being, lack decent housing and are exploited by middlemen. Deprived of all security, they live under such personal servitude that almost every opportunity of acting on their own initiative and responsibility is denied to them and all advancement in human culture and all sharing in social and political life is forbidden to them. According to the different cases, therefore, reforms are necessary: that income may grow, working conditions should be improved, security in employment increased, and an incentive to working on one’s own initiative given. Indeed, insufficiently cultivated estates should be distributed to those who can make these lands fruitful; in this case, the necessary things and means, especially educational aids and the right facilities for cooperative organization, must be supplied. Whenever, nevertheless, the common good requires expropriation, compensation must be reckoned in equity after all the circumstances have been weighed.