Don’t make the Pharisaical mistake of interpreting Catholic laws to extremes. Take them in consideration of the whole body of laws, not out of context.
Legitimate defense
2263 The legitimate defense of persons and societies is not an exception to the prohibition against the murder of the innocent that constitutes intentional killing. "The act of self-defense can have a double effect: the preservation of one’s own life; and the killing of the aggressor. . . . The one is intended, the other is not."65
2264 Love toward oneself remains a fundamental principle of morality. Therefore it is legitimate to insist on respect for one’s own right to life. **Someone who defends his life is not guilty of murder even if he is forced to deal his aggressor a lethal blow:
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If a man in self-defense uses more than necessary violence, it will be unlawful: whereas if he repels force with moderation, his defense will be lawful. . . . Nor is it necessary for salvation that a man omit the act of moderate self-defense to avoid killing the other man, since one is bound to take more care of one’s own life than of another’s.66
2265 Legitimate defense can be not only a right but a grave duty for one who is responsible for the lives of others. The defense of the common good requires that an unjust aggressor be rendered unable to cause harm. For this reason, those who legitimately hold authority also have the right to use arms to repel aggressors against the civil community entrusted to their responsibility.
Bold emphasis mine.
What does this mean to anyone here? Next time a Nazi knocks on your door asking you “yes or no, Jews here?” do you think it’s impermissible to lie and say no? Instead, you’ll shoot them, because that’s permissible? You’re kidding me.
Furthermore, the reason lying is bad is because it causes others to become deceived, not because it’s “categorically false”. Therefore, if I have stole money from my friend and another asked me “did you steal from your friend?” and I, incredulously exclaim “Yeah of course. I of all people stole from my own friend!” will you then say “hey, no big deal, he told the truth, just no one believed him!” No, for crying out loud, people!!! It’s a LIE even if it is true, because of the INTENT behind it (that is, to deceive by incredulity)