This is jury tampering. As long as violence is not involved, it is only a misdemeanor punishable by a $1000 fine in my state

Every legal mind has been very clear that jurors should not be told about it; people who know about nullification explicitly rely more on their feelings than evidence and are more easily fooled by sympathetic defendants and vice versa. Nullification works both ways, you could convinct without reasonable doubt or evidence, which is also not black and white.

Nullification exists simply because jurors can't be prosecuted for getting it wrong, so they can do whatever they want. But if you join intending to nullify, you technically commited purgery when you swore to "uphold the law". It's a very grey area because we technically want jurors to make informed and fair decisions, not selfish ones. Courts have been clear it shouldn't be explicitly mentioned, but they also haven't banned it because they believe in the idea of everyone coming to the conclusion the law doesn't apply/he isn't guilty of the crime despite clearly doing the thing, rather than declaring him "guilty without punishment". It would be difficult to ban or make a law against this too. They're just saying the law doesn't apply in this case which is reasonable.

Of course in the case of luigi I would totally agree with them letting him walk, but nullification is a fragile thing, especially for those who need to be told directly they have that power. Plus, luigi will at best get a reduced sentence like in crimes of "passion" or for being in a crisis, he likely isn't going to walk.

Edit: I think we can get banned for discussing this, i don't know anymore.