The Euthyphro Dilemma sets theist with a Dilemma. Is God’s will good because he wills it, or because it appeals to an outside standard of goodness? The Christian takes this to be that Goodness is grounded in God’s being or nature. The issue that arises from that is that people push the issue to another problem: What does it mean to say God is good? Does that mean God is God? Does goodness lose all meaning? The way Christians get around this issue is that when we say “God is good” we are saying not that “God is God” but rather that God is the moral standard that we ought to live in reference to. He is the Archetypal Good and we deal with Ectypal good. The issue being dealt with raises another question: Why does God have these properties over against another set of attributes? Are these attributes good because God possesses them or are they good apart from God? The way the Christian gets around this is that God is by Divine Simplicity. God is co-referential to his attributes. These are not parts that makeup God but are him. They are necessary and not contingent.
God is not an abstraction, but rather a person that reveals his character. That gives us the content of our norms and obligations. So, I think God ground objective ethics and anyone that rejects that has a dilemma of their own: They are either a realist or non-realist(ignoring quasi-realist) when it comes to ethics. If they are a realist, then they can’t accept this argument because it reduces to an infinite regress. If they are an anti-realist, then they have to give up rationality.