There is a causal connection between this and the previous verse. Verse 2 gives the basis for affirmation that there is no condemnation now for those who live in union with Christ Jesus.
In the phrase law of the Spirit, the word law is used in a way similar to its use in 7.21, 23. In fact, Paul uses the phrase law of the Spirit (rather than simply saying “the Spirit”) because of his use of the same term in the previous chapter. Law of the Spirit possibly means for Paul something like “power of the Spirit” or “rule of the Spirit.” However, for the sake of the relation of this expression to the previous chapter, it is important to use the same word in both places, provided, of course, that there is no distortion of meaning. In many languages one cannot speak of the law of the Spirit, but one can indicate something of the contrast between the action of the Spirit and that of sin and death by translating “being controlled by the Spirit has freed me from the control of sin and death” or “… has set me free, and therefore sin and death do not control me.”
“Spirit of life” is taken by most commentators to mean the Spirit, which brings us life (see New English Bible “the life-giving law of the Spirit”). Which brings us life may be rendered as “which causes us to really live.” It may be necessary to include an expression such as “really” or “truly” in order to indicate that this life is not merely a matter of human existence but has a distinctive quality.
Life in union with Christ Jesus indicates a special quality of life. One may therefore translate as “causes us to really live in union with Christ Jesus” or “causes us to really live, being joined closely to Christ Jesus.”
Some Greek manuscripts read “you” (singular) in place of me of this verse, while still other manuscripts read “us.” The use of the inclusive pronoun “us” was doubtless introduced by some scribe who thought that both Paul and his readers should be included, but the choice between me and “you” is not so easy. The UBS Greek text suggests me, though rating this a “C” decision, indicating a high probability of doubt regarding the original reading. Most modern translators appear to accept me, assuming that it is more probable that a scribe would have changed the text from me to “you,” than the other way around.
Paul continues his play on the word law in the phrase the law of sin and death. He could just as easily have said, “the Spirit has set me free from sin and death.” If one can retain law in this context, it may be possible to translate as “the law which declares sin and death,” “the law which shows sin and death,” or “the law which causes sin and death.”
Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on Paul’s Letter to the Romans. (UBS Handbook Series). New York: UBS, 1973. For this and other handbooks for translators see here .