"Tainted rewrite" isn't a legal concept either. You have to prove (on balance of probabilities - more likely than not) that the defendant made an unauthorized copy, made an unauthorized derivative work, etc. Clean-room rewriting is a defense strategy, because if the programmer never saw the original work, they couldn't possibly have made a derivative. But even without that, you still have to prove they did. It's not an offence to just not be able to prove you didn't break the law.
If you wanted to do the clean-room approach for something like chardet in a less controversial way, instead of having the AI do all the work couldn’t the AI generate the spec and then a human (with no exposure to the original code) do an initial implementation based on the spec?
