Romans 8:1-4

Without the cross there would always be the problem of punishment. No matter how well we managed to live now, there would be the problem of what we had done in the past. Moreover, one failure and that would be it. But in Christ there is now no condemnation.

The Greek word used for condemnation here means more "punishment following sentence" than just "condemnation". Chapter 7 has described a life where the desire to be good leads only to condemnation because of perpetual failure. In Christ we can be free of this. If we live by law (seeking to attain a standard by our own efforts) we are subject to sin and death. Ie we will sin, and we will fail. In Christ things can be different, we can be different, our life can be different.

Law was powerless to make this happen. Although it set out wonderful guidelines and rules, it was doomed to failure because of our sin. So God sent His Son "in the likeness of sinful flesh". Ie Jesus was fully human, and he was fully subject to the same temptations that we are subject to (Heb 2:18, 4:15). Yes Jesus was without sin, so He was a perfect sin offering, and the full price of sin was paid for on the cross. The full price of your guilt and my guilt was paid for on the cross.

"So that the righteous requirement of the law might be fully met in us who live not according to the flesh, but according to the Spirit". What does this mean? There are two ways in which the righteous requirements of the law are met in us who live by the Spirit":

1. The price of sin has been fully paid.
2. It is possible for us to live a life that is pleasing to God. Now we will never be perfect this side of eternity, but it is possible for us to live a life of freedom and fruitfulness.

If continue to live by the flesh (by human effort) then neither of these two things can be true. For we are depending upon our own efforts to justify ourselves, which we can never do, and will be subject to the failings described in Chapter 7.