Justice is a different story: human law has every business enforcing justice to the best of its ability. Justice does not have to be left to work itself out in the heart of each individual.
If someone owes me a thousand dollars, has it to spare, but refuses to pay it, I sure would want there to be a judge who will force him to pay me. And, strictly speaking, I don't even need a thousand dollars right now (though I could certainly use it).
How then can I object to the principle of a judge who would force someone, who has the means but does not act on them, to give clean drinking water to those who don't have it?
Granted, figuring out who is owed what is a lot more straightforward with written contracts and the like than with the rich, collectively, and the poor, collectively (though it's not always just to enforce a written contract). Any particular attempt to enforce the justice of a rich man meeting a poor man's needs -- I might as well call it what it is: redistrubution -- may itself fall short of justice, in all sorts of ways. It might even be the case that, given the condition of a particular society, attempting to make or enforce redistrubution laws would be contrary to the public good.
Still, it seems that one of the following must be true:
The Church is wrong to teach that excess wealth belongs in justice to the poor.
A concern that justice be done by and to the members of a society is outside the legitimate scope of human law.
Laws governing the redistribution of wealth are, in principle, within the legitimate scope of human law.