Scripture confirms that the law of God is eternal. See Isaiah 66:23, Psalms 19:7-14, and Psalms 119:160 for statements of fact.
The Bible shows us that God has an eternal standard for all of His creation. It is found in the war in heaven where Lucifer and a third of the angels fell because of sin, but two thirds did not. It is found in Eden where Adam and Eve lived in harmony with God before falling into sin. It is found in thousands of years of God's efforts to save man, even going so far as to send His only Son to die on the cross. It is found in the everlasting gospel. It is found in the patience of the saints who keep the commandments of God. It is found in Isaiah's description of the new heaven and new earth.
If you think about it, if God was going to change His standard, he could have done so at the very beginning, when there was war in heaven. He could have done so when Adam and Eve sinned. He could have done so any time in the thousands of years of sinful man, but He did not, He instead wrote His law in stone with His own hand.
God goes to great lengths in the Bible to call man to obedience unto righteousness. If God were to change His standard, the goal post moves forward or backward, and the whole of salvation and the cross are rendered moot.
The point of salvation is reconciliation with God, according to His standard. Sin is and always will be transgression of the eternal law of God. It has to be an unchanging standard, otherwise it's not a standard at all.
