Why couldn't it? I don't think that you're correct here--the 14th Amendment prevents a state from depriving a person of due process. I don't see why if a state chose to repeal its laws against murder how it would be denying anyone due process. Do you care to elaborate?
You may be Constitutionally correct. If California were to suddenly declare murder to be legal, I don’t see where in the Constitution my sense of moral outrage entitles me to use Congress to make decisions for them.