This is no license to sin

Already in [Romans] 5:12–21 there are indications that the Christ-gift is not morally vacuous, an unconditional gift that winks at human sin: it contains transformative power. The recipients of this grace are said to receive the gift of righteousness (5:17) and to be constituted righteous (5:19): where sin once reigned, now grace reigns “through righteousness” to bring about eternal life (5:21). The language of “reigning” (βασιλεύω) figures grace as a counteracting power whose authority replaces that of sin; far from offering a license for sin, the Christ-gift establishes an alternative regime of power.—J. M. G. Barclay, Paul and the Gift, 497