Well this is a criminal trial. A juror’s decision is either one of two choices: 1) guilty; 2) not guilty.
Let me clarify that for you then... in context of what you said. If the guy is "guilty" of the crime as specified by the law (and you say that the defendant is either determined to be guilty or not guilty according to that law) -- I'm saying that if you, as a juror, see that law as unjust -- then you vote "Not Guilty" -- even though you see that he was "guilty" according to that specified law.
I hope that's clearer and shows how the "determination" goes further than simply "guilty or not guilty" according to just that law. And any juror can do that and no one can do anything about it.
Its not my place as a juror to determine if a law is just or not.
That is for the judicial branch to decide.