Instructions are advisory. They are meant to help jurors who are unclear of what the law says. However, they are not shackles on the jurors. Jurors are free to ignore them, and should ignore them when justice requires it.

For example, Jurors have the right to find a guy not guilty when caught red handed with marijuana simply because the law is unconstitutional. They have that right and that is intentional in our system. Judges on the other hand, tell jurors in their instructions that they "have to find them guilty if they believe he possessed the drugs". When judges do this, I consider it jury tampering, and unfortunately for innocent pot smokers, too many jurors listen to the instructions.