[quote=DavidJoseph]the current catechism says that it’s not lying to withhold the truth from somebody who has no right to the truth (telling the Nazis you’re not hiding any Jews when you really are doing so comes to mind)
2482 **“A lie consists in speaking a falsehood with the intention of deceiving.”**281 The Lord denounces lying as the work of the devil: "You are of your father the devil, … there is no truth in him. When he lies, he speaks according to his own nature, for he is a liar and the father of lies."282
2483 Lying is the most direct offense against the truth. To lie is to speak or act against the truth in order to lead someone into error. By injuring man’s relation to truth and to his neighbor, a lie offends against the fundamental relation of man and of his word to the Lord.
2485 By its very nature, lying is to be condemned. It is a profanation of speech, whereas the purpose of speech is to communicate known truth to others. The deliberate intention of leading a neighbor into error by saying things contrary to the truth constitutes a failure in justice and charity. The culpability is greater when the intention of deceiving entails the risk of deadly consequences for those who are led astray.
2489 Charity and respect for the truth should dictate the response to every request for information or communication. The good and safety of others, respect for privacy, and the common good are sufficient reasons for being silent about what ought not be known or for making use of a discreet language. The duty to avoid scandal often commands strict discretion. No one is bound to reveal the truth to someone who does not have the right to know it.
2508 Lying consists in saying what is false with the intention of deceiving one’s neighbor.
Note that #2489 offers the options of silence or discreet language, but not of lying as defined in #2482, “speaking a falsehood with the intention of deceiving”, or in #2508, “saying what is false with the intention of deceiving one’s neighbor”. So, whoever claimed that about the new Catechism was mistaken. The only way that telling the Nazis that you have no Jews in your house could be justified morally is under an idea like that of Cataneo, quoted in Newman, Apologia pro Vita Sua p. 456-7:
In such and similar cases, in which your sincerity is unjustly assailed, when no other way more prompt or more efficacious presents itself, and when it is not enough to say, ‘I do not know,’ let such persons be met openly with a downright resolute ‘No’ without thinking upon any thing else. For such a ‘No’ is conformable to the universal opinion of men, who are the judges of words, and who certainly have not placed upon them obligations to the injury of the Human Republic, nor ever entered into a compact to use them in behalf of rascals, spies, incendiaries, and thieves. I repeat that such a ‘No’ is conformable to the universal mind of man, and with this mind your own mind ought to be in union and alliance. Who does not see the manifest advantage which highway robbers would derive, were travellers when asked if they had gold, jewels, &c., obliged either to invent tergiversations or to answer ‘Yes, we have?’ Accordingly in such circumstances that ‘No’ which you utter [see Card. Pallav. lib. iii. c. xi. n. 23, de Fide, Spe, &c.] remains deprived of its proper meaning, and is like a piece of coin, from which by the command of the government the current value has been withdrawn, so that by using it you become in no sense guilty of lying.
This is not, however, asserted in the Catechism, but remains an opinion neither taught nor rejected by the Church, and if the Church were to teach it, she would have a considerable tradition behind her, Newman’s discussion of which you may wish to consult here - such traditionalists would have no basis to stand on.