Jury nullification is a specific term[1] referring to when a jury knows that a particular defendant is guilty of a crime but they decide to find them not guilty because they believe the law to be unjust. There are many examples of this occurring in history, and this exists as a unwritten legal concept as a logical consequence of two explicit legal concepts:

* Juries cannot be punished or reprimanded for coming to the "wrong decision". * A defendant who is acquitted cannot be tried again in front of a jury because of the defense of double jeopardy.

[1]: https://en.wikipedia.org/wiki/Jury_nullification

when somebody technically violated the law, but there's reasonable doubt, it's not nullification

I'm not talking about when there is doubt... I'm literally talking about jury nullification. Why do you keep insisting on setting it up as though I'm saying something else?