If there is no law, there is no accounting for disobedience or sin.
  • sin is not taken into account when there is no law. - Romans 5:13
We need to know what is not allowed in any given system or structure before acting contrary and therefore sinning.  And sometimes it does not even take acting on the knowledge - 
  • "You have heard that it was said, 'Do not commit adultery.' But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart. - Matthew 5:27-28
Before humanity, when it was just God and His angels, all heavenly beings recognized God as The Law. Lucifer desired to usurp The Law with his forceful declarations of "I will..." that are documented in Isaiah 14:13-14.  This rebellion did not work for him so after his fall he saw an opportunity to strike back at God by tempting God's created image - humans - to disobey/sin and have that sin-nature enter the world.

God The Law or Lawgiver issues a Law/command to His creation - 
  • And the LORD God commanded the man, "You are free to eat from any tree in the garden; but you must not eat from the tree of the knowledge of good and evil, for when you eat of it you will surely die." - Genesis 2:16-17
Humanity fails to obey this command.  Sin/disobedience/rebellion enters and exists before The Law (of Moses) - 
  • for before the law was given, sin was in the world. - Romans 5:13
The law was added so that the trespass might increase. But where sin increased, grace increased all the more, so that, just as sin reigned in death, so also grace might reign through righteousness to bring eternal life through Jesus Christ our Lord.  That was Romans 5:20-21.

The added "law" was The Law of Moses.  The "trespass" that "might increase" was the original sin or disobedience.  However, in every conceivable instance where disobedience/rebellion against God occurred, the Lord's unmerited favor not only increased, but increased "all the more"!  Why?  "so that just as sin and death" walk hand-in-hand with each other, so also the undeserving favor of God "might reign" through the right standing of Christ Jesus in order to bring all who believe in Him eternal life. [Pritchard Paraphrase]

Just label me...A Graced Man!