You are your own supreme authority because GOD gave you a free will. Free will is the ability to deside for yourself what you want to do and how you want to live. You choose what you believe about everything.
Adam, by diobeying GOD and eating of the Tree of Knowledge of Good and Evil gave us the genetic disposition to know the difference between good and evil (right and wrong). There was no evil in the Garden, that is why GOD drove Adam and Eve out (yes the devil is evil and he was there, but that is a different discussion). Disobedience leads to evil behavior.
There is no true righteousness in us, because our natural righteousness is selfrighteousness. That is why to serve GOD, to obey GOD we must die to ourself. We have to stop being our own supreme authority and makeGODour surpeme authority. To give up our will or right to decide how to live our life is a death that Jesus tells us gives us life, if we die to ourself and allow GOD to live our life for us. We could die to ourself for a false god or religion, but there is no resurrection power or life. Only the True and Living GOD, Jehovah has the power to create life and only Jehovah has the power to give resurrection life. No religion or failth in anything other then the completed work of Christ can give us life and only by making (not allowing but making by an act of will) GOD our supreme authority can we live that life. Because He will give us His Holy Spirit who makes us the righteousness of GOD in Christ Jesus.
The sad thing is there are people who want to and think they are serving GOD, but at the judgement He will say, I do no even know you. Because they have not made Him their supreme authority.I know, Iwas one of those for a long time.
We do not know or understand GOD if we ask why? Why did He tell the Isrealites to kill the men, women, and children, even their animals? Why did He destroy the world in the great flood? Why do good thing happen to bad people? Why do bad things happen to good people? Why are there wars and famine?
He is the creater (owner) of all things that exist. He is the sustainer of all life, human, animal, plant, spiritual! He made man with a free will which is the ability and responsibility to choose what he will do and how he will do it. We must make Him our Supreme Authority and die to ourself so that He can manifist His Kingdom in the earth through us.