Paul had last concluded that he had been a wretched man, serving sin with his flesh even though his will and mind wanted to serve Torah. But he thanked God through Messiah Yeshua for His deliverance.
Romans 8:1-4 (KJV)
There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
In summary for chapter 7, Paul said that there is no longer any condemnation from the Torah for those who are in Yeshua, those who do not walk after the flesh, but walk according to the Holy Spirit (verse 1). Once someone has become a believer by repentance and faith in Yeshua, the condemnation that results from not following the Torah is gone and the believer can walk in fellowship with Yeshua through the indwelling of the Holy Spirit and is enabled to follow Torah rather than live and act according to the fleshly nature.
Verse 2 is somewhat of a restatement of verse 1. Paul was saying that the "law of the Spirit of life in Yeshua" is that power by which the believer is saved and is enabled to live according to the Torah. It is that power that has made the believer free from the "law of sin and death" (the law whereby death results from sin and the inability to follow Torah).
The Torah could not make man righteous, because of the inability of the flesh (verse 3). But when God sent His own Son (Yeshua) in human form, He defeated sin that reigned in the flesh.
It is through Yeshua that the righteousness of Torah can be fulfilled in the believer (verse 4). Again, Paul added that the believer does not walk by flesh, but by the empowering Holy Spirit.
Notice that by walking according to the Spirit, Torah is fulfilled. It doesn't mean that the Torah is then over and done with. Torah can never be fulfilled in the sense that once it is done, it can be set aside. The believer's life is to be characterized by Torah living. It the the Holy Spirit's function to enable the believer to obey the Torah. How blessed believers are!