[black_puppydog]

Fair point, not sure why you're being downvoted...

I would never dream to equate proprietary documentation to Nazi war crimes. That's without question. I just used this because, like so often, in questions about these war crimes, there is no real argument to be made for "the other side" so it clearly shows the line of reasoning for breaking with a legal convention in specific cases. You said it yourself: "it's something so intrinsically evil that you can't rely on pure formality." Which is exactly the point. Protecting the perpetrator just because there's also a value in relying on their actions being legal at the time just doesn't outweigh the cost of letting them get away with such monstrosities.

A more recent and less evil example would actually be the Cum-Ex scandal. One question was whether money would have to be given back, given that what happened might be technically-legal but blatantly, and expressly against the spirit/intention of the law. But that whole thing is still being fought out so the conclusion is less clear cut.