Here law, the Spirit, and life are in contrast to law, sin, and death. The two laws are in opposition to each other, the Spirit is in opposition to sin, and life is in opposition to death. In Rom. 5 grace, which is God embodied in us, is in opposition to sin, which is Satan embodied in us (Rom. 5:21). In Rom. 8 the Spirit, who is God living in us, is in opposition to sin. Thus, the grace in ch. 5 is the Spirit in ch. 8, the very God embodied in us as grace, living and acting in us.
In the previous chapters life is mentioned a number of times (Rom. 1:17; 2:7; 5:10, 17-18, 21; 6:4, 22-23). In this chapter life is joined with the Spirit in the phrase the Spirit of life, showing that everything regarding life in the preceding chapters is included in the Spirit in this chapter. Life belongs to the Spirit, and the Spirit is of life. These two are actually one (John 6:63). The way to experience the divine, eternal, uncreated life is by the Spirit of life.