Do you know that a Walk after the Spirit will lead you to keep and obey the law of God, in order He might fulfill the righteousness of the law in you. When will you come to this realization?
The whole of Romans chapter 7 is telling us about a law of sin and death in our body, which originated to the carnal mind, which is enmity against God for it is not subject to the law of God, keeping us doing what evil is, despite we want to do what good is, because we have no power to do it from our own. The remedy found in Christ. Having His mind that replaced our carnal mind, we will be brought in to subjection to the law of God.
Which mind? The mind of Christ, for it is impossible with his carnal mind.
Take attention on what Paul said: "With the mind I my self serve the law of God." (Romans 7:25), After serving the law, he came in harmony with the law demands and just then, "there is no condemnation for those who are in Christ Jesus, who do not walk according to the flesh but according to the Spirit" (Romans 8:1). Serving the law is walking after the Spirit.
The spirit of life in Christ Jesus, the Holy Spirit that resides in Paul's mind replacing the carnal mind, released him from the law of sin and death that dominate him, which originated from his carnal mind, and further enable him to serve the law of God (Romans 8:2), this makes him not under condemnation of the law.
But without the mind of Christ, the flesh could not produce righteousness and the law could not justify him, this makes all men comes under condemnation of the law. God send Christ in the likeness of sinful flesh, and with his perfect obedience, he condemn, he conquered, he over ruled the power of sin in him (Romans 8:3).
This is an example for us, that if we walk as He had walked, having His mind and walk after the Holy Spirit, we too might condemn the sin in us, and from a man that was not subject to the law of God, we becomes those who has the righteousness of the law in us (Romans 8:4).