The Son of God came to destroy sinning. The enemy on the rebel planet is sin. The deadly virus in the Appalachian village is sin. The force to be conquered on the Western Front is sin. Christmas is God's invasion of enemy territory to rescue a people from the devil and destroy the sin in their lives.
Sin is lawlessness.
The law in John's mind here is not the U.S. Constitution. It is God's law. It's the expression of God's revealed will for his creatures. Lawlessness is living as though your own ideas are superior to God's. Lawlessness replaces God's law with my contrary desires.