The Decrees of God are His eternal purpose, according to His will, whereby He has foreordained whatever comes to pass. His Decrees do not negate the responsibility of people for their sins, nor does it mean that God is responsible for sin. But, it necessarily is true that God knows all things actual as well as potential and that which exists exists due to His creative effort. It also follows that God has eternally known all events that have occurred, are occurring and will occur in this creation including the fall, redemption, glorification, etc. Yet, God is not the one responsible for the sin in the world but has decreed by His permission that it be allowed to exist. Isaiah 46:9-10 says,
"Remember the former things long past, for I am God, and there is no other; I am God, and there is no one like Me, Declaring the end from the beginning and from ancient times things which have not been done, saying, ‘My purpose will be established, and I will accomplish all My good pleasure."
God's efficacious decrees are those decrees which God has purposed and determined to occur, i.e., Acts 2:23 "this Man, delivered up by the predetermined plan and foreknowledge of God, you nailed to a cross by the hands of godless men and put Him to death." God's permissive decrees are those decrees where He permits things to occur, such as evil.