as disobeying God and his laws.

Let me give you an example:

The Perfect World (Garden Of Eden) Adam and Eve were told they could do anything, except eat the fruit of the tree of knowledge of good and evil. What did they do? They disobeyed God and ate it anyway, in doing so, they Sinned. God did this to show that people will sin even in a perfect world, and that his other creations (Angels, Fallen Angels) would interfer even in a person world (taking the form of a snake).

Perhaps you forgot the Ten Commandments written by God onto stone and handed to Moses? You know, the ones saying a lot of "Thou Shalt Not", etc. Like "Thou shalt not steal" "Thou Shalt Not Commit Adultry", etc, the ones that people ignore anyway. Breaking these commandments is a sin. Then there is Mosaic Law, etc. Without these, people are lawless and become b*tches and b*stards and the world becomes Hell.