We are not born under the law. We are born into the world without the benefit of law, unless our parents bring us intentionally into the Rule (Kingdom) of God. That is the real mark of infant baptism, that the parents and godparents and community of the church are promising to bring a child up within the church and kingdom of God. That is why we don't rush that commitment.
But whether we are born in the wilds or in the house of God, we all learn quickly how to live in a world of sin. We sin, that is we miss the mark of living into the purpose and desire of God for us. Often people wince at saying that children sin, but no one has to be taught how to hit or be selfish.
We are creatures who must be born of flesh and of water as Jesus told Nicodemus in John's Gospel. We sin, but we are able through the Spirit of God to return to our original purpose of living as God's image in the world (Genesis 2) and God's sons and daughters (John 1).
When we fail to live into that fullness of purpose, we are sinning. We have the law to guide us when we are young, and it is not done away with in Christ, as he said in Matthew 5, but rather it is fulfilled, and as we mature we no longer need it. This is just as it is in life. When we are young we are taught not to steal, but as we mature we no longer need to be told, rather our life moves to easy compliance with the law and then past that to generative creative giving. We no longer feel even desire to steal but rather we freely give to others knowing that as God's children we have all our needs fulfilled in Christ.
Our sins should, legally speaking, disqualify us from life in God because we have rejected and left God's purpose and desire for us. The news bears witness to our state as humanity, as a nation, as people. Our hearts bear witness to our own failures. If they do not, our families and communities can surely name our sins for us! We have not loved God or our neighbors as ourselves. We have done wrong and left good undone.
But God did not abandon us, but rather sent his Son a person of his own essence to bear our sins and death sentence and offer to us his own Rule of Life, new life and creation through his death and resurrection. We are made new in him. We join ourselves to him in baptism, being reborn. The consequences of our sin and our sins then is washed away. We are made free (redeemed) to choose to live in this new life and mature into the full stature of Christ.
This is where it begins. We weekly (or more) reenact our oneness in Christ in consuming his body and blood in the Eucharist, the thanksgiving meal and remembrance of passion and new life. We are made one again weekly in the Lord's Supper, Mass, Communion. But our entrance is the waters of baptism.