In the Socratic/Platonic/Aristotelian most high God paradigm this is trivially simple. Good is logically equivalent to that which God approves of (see Euthyphro

In the Socratic/Platonic/Aristotelian most high God paradigm this is trivially simple. Good is logically equivalent to that which God approves of (see Euthyphro). Thus by the definition of free will it’s a logical consequence that it’s possible for creatures to do things that God doesn’t approve of, which is to say do evil. God permits but does not approve.