Yes, jurors are the supreme arbiter of the law. I shudder to think of the alternatives.
We're talking nullifcation here, and it only takes one juror, just one to nullify a jury. Sorry, but that only works when you have 12 people who are dilligently applying the law. As soon as you get one yahoo in who thinks that all gun laws are evil, all black men just go free, that Mexican can do no wrong, or any other such scenerio it all falls apart.