Who decides what is morally wrong? If everyone decided to not follow or enforce laws based on their own morals, society would be in absolute chaos. You can't have a functioning society around "I do what I believe, fuck y'all"
People ultimately decide on their own. There are institutions that make judgments but ultimate it's an individual that decides. But for a lot of things, there are nearly universal agreement going one way, e.g. everyone almost universally agrees that murder is wrong.