Two points . . .

(1) Last I heard, the Constitution is still the supreme law in the United States, and therefore is still the current law, even if laws more recently written attempt to ignore it.

(2) The intention of the writers of the Constitution was that jurors would vote their conscience, so voting one's conscience would hopefully not contradict voting for what is Constitutional - although I suppose there are those who would vote to convict someone for an unconstitutional law because they believe that, say, eating meat is bad or whatever.

I would hope that any adult on a jury would understand that they cast their vote for "not guilty" if they believe the defendant either did not commit the crime in question OR if they believe the law is faulty, and that they should vote "guilty" only if they believe the law is just and lawful and applicable to the situation and that the defendant broke that law in a way that a reasonable person would not.

(Of course, every situation is different, which is why I go on at some length in my description. For example, a law against breaking and entering and a law against theft are both good laws - however, if the only way to get the necessary medical supplies in time to save a person's life is to break into a pharmacy and steal what is needed, I would hope that no jury would find the "perpetrator" guilty. Of course, even most prosecutors would not take such a case to a jury because they would know that they would lose.)