...using Hume's is-ought distinction's mirror concept, the ought-is distinction***.
Euthyphro's dilemma: "Is the pious loved by the gods because it is pious? Or is it pious because it is loved by the gods?" This can be reworded to read "Is the good commanded by God because it is good? Or is it good because it is commanded by God?" The first question addresses theistic natural law theory, and the second question addresses divine command theory.
Natural law theory: "Is the pious loved by the gods because it is pious?" God commands whatever is good despite his commanding it. Because this good (which anyone can justify using reason) does not correspond to perfect being, it commits the ought-is fallacy. According to this theory, good is over God.
Divine command theory: "Or is it pious because it is loved by the gods?" Good is whatever God commands. Because this good does not correspond to perfect being and God makes it up, it also commits the ought-is fallacy. If you say that "God's commands are good because God exists" you commit the is-ought fallacy. According to this theory, God is over good.
Synthesis: God commands in accordance with His good nature/essence. Good is good despite God's command and anyone can reason to it, but it corresponds to perfect being (God). For the sake of argument, if no God exists, all good-concepts correspond to nothing and commit the ought-is fallacy, and using this synthesis to argue for good's or God's existence commits the ought-is fallacy. Again, if you say that "Good is good because God exists" you commit the is-ought fallacy. According to this synthesis, God is good.
At the bottom of this relevant link are more relevant links going into more detail without using the words "natural law" or "divine command".
***Hume's is-ought (existence-justification) distinction says you cannot use the existence of the status quo (the way things are) to justify (belief in) the status quo—1) just because we have a natural inclination to act a certain way does not mean it is a good thing to do, and 2) just because the sun rises and sets every morning does not mean we have a good theory about sunrises and sunsets (we may believe the sun revolves around the earth!). Flipped around, the ought-is (justification-existence) distinction says you cannot say something (good, God, or anything else) exists just because its existence is justified (iow, just because you have reasons to believe, or to want to believe, it exists)—sometimes we are wrong about something even though we have good reasons to think we are right. This is true about things we do, and about things we 'think' we know.
In order to avoid the is-ought/ought-is problem, our belief (about good, God or anything else) must both be justified and correspond to reality.