In contrast to the one who is pure, the one who makes a practice of sinning is practicing lawlessness (3:4). The word lawless evokes memories of the old west, people living without restraint and making their own rules. The old west bad guy might “make it a habit to be bad.”
In the Greek Old Testament, the word ἀνομία meant far more than breaking the Mosaic Law. It has the sense of disdain for the Law. In classical Greek the noun had the connotation of the denial of a law (Brill DAG). Those who are lawless believe they are not under the authority of the law. For example, when the state of Michigan passed the seatbelt law, many people simply ignored it and lived as if that law did not apply to them. They lived in denial of the clear command of the state government (until the police started writing tickets for not wearing your seatbelt).
Applied to a theological idea like Jesus is the Messiah, the opponents certainly know this is what John has said in his Gospel, but they deny that it is valid and they reject that teaching as having any impact for their lives. I might read an essay on the importance of going to confession and doing penance in the Catholic tradition. I can hear the words and understand what they are saying, but I will deny that it has anything to do with me as a Protestant.
The opponents seem to say that since Jesus has died on the cross and fulfilled God’s Law, God’s Law no longer any authority over them. If (as Paul says) we are free from the Law, then what the Law said was sin is no longer sin. If a kid who is a day short of his twenty-first birthday buys cigarettes and alcohol, then they are breaking the law. But if they wait a day and buy it after their birthday, that law no longer has any authority over them and they are free to drink and smoke legally. The opponents are simply saying if the Law is fulfilled in Jesus, then the old laws do not apply anymore. They can “drink and smoke” all they want since they are not under those old laws.
Karen Jobes points to Leviticus 26:43 as an example of the use of the world in the Septuagint. To be lawless is to have disdain for the Law of God, to knowingly suppress the clear revelation of God and do what he has said “ought not be done” (1, 2, & 3 John, 143). This is not far from Paul’s description of the human race in Romans 1:18-32.
In the context of eschatological judgment, it is possible John knew the teaching of Jesus in the conclusion to the Sermon on the Mount (Matthew 7:21). When the many who did miracles in the name of Jesus come before the Son of Man at the judgement at the time of the second coming, Jesus will send them away into the darkness where there is gnashing of teeth, saying “I never knew you, away from men you evildoers (ἀνομία).
Is this a reference to the opponents who have gone out from John’s churches? Likely, they are denying the clear revelation of God’s word through the witness, the last of the Apostles, John. They know what John has said about Jesus and they are simply denying it as valid for them.
Since Jesus has dealt with sin, the one who remains in Jesus does not make a practice of sinning (3:5-6). This is the second “appearing” of Jesus in this section of 1 John. In 2:28, the word refers to the future appearing of Jesus in judgment. Here the word refers to the incarnation, he appeared to take away sin.
Since Jesus has no sin, the one who is abiding in him should not keep on sinning. In the context of these verses, John is making a contrast with the ones who are lawless, who deny that God’s clear revelation has any authority over their lives. For the one who is remaining in Christ, it is impossible to think God’s revelation has no authority over them!
The grammar is once again very important for understanding the practical theology of this verse. The Greek phrase καὶ οὐ δύναται ἁμαρτάνειν can be understood as “he is not able to sin,” of “and he cannot sin” (KJV). This sounds like the opponents as I suggested above. But the present tense verbs are usually taken here as continuous, so that most modern translations say no one who abides/remains in Jesus will “keep on sinning” (as in the NIV, ESV).
The argument John makes is also based on the nature of Jesus: he took sin away and he himself had no sin, so those who are so closely associated with Jesus that they can be called the children of God (as he is the son of God) ought to live a life without sin.