Of course you don't need a CoC to enforce anything! You can moderate aggressively without one. What it does is sets expectations. It sets expectations for ever

Of course you don't need a CoC to enforce anything! You can moderate aggressively without one. What it does is sets expectations. It sets expectations for everyone involved in any interactions. In general, this should give you confidence that there will be some moderation or recourse if you experience rude behavior. That may allow some people who have been burned by ruder communities to be willing to give yours a try.