That passage is talking about God's Judgement on us, and how He views sin. With Jesus' death, He no longer judges us by the Law, but by grace.
Our law, and how we keep society civil has not changed. He provided for us to execute murderers, and it was not revoked in the New Testament.
Anything NOT revoked is still in force. Hence, we still keep the 10 Commandments.
And I supposed you keep them, right? Just like the Pharisees. Oh, wait a minute, didn't Jesus say the Pharisees were hypocrites who pretended to keep the law but didn't?
Better prayerfully and carefully re-read Romans and Galatians for the doctrine of the Gospel of the Grace of Christ (no law - Romans 6:14), and re-read Hebrews for the doctrine of the New Covenant of Grace which did away with the Old Covenant of the Law.
There's only two things that defeat sin: death (Romans 6:7) and grace (Romans 6:14) and Jesus did both for us.