So getting back to the OP, under the New Covenant man is still under obligation-to righteousness, to obedience, to the Law, but that obligation is now shown to be authentically fulfilled only as per Rom 13:8-10. And man is only able to fulfill it by means of his communion with God, apart from Whom he can do nothing, but with Whom all things are possible. This communion was made possible by Jesus's work of atonement/reconciliation on the cross whereby man is redeemed, and can now approach God, by faith, by means of which this communion is established, or reestablished, as it was originally shattered at the Fall.
The New Covenant: "'Thou Shalt Love'- and only I, God, can accomplish this work in you, if you hear My voice and answer My call." It's not about God suddenly ignoring His justice, but rather about Him restoring it, the right way, in due time.