Paul designates two separate types of law. The first is referred to as the law of the spirit of life, and the second is referred to as the law of sin. The word for law, is a general reference to the rules or commands or influence, by which our life is governed.
The law of sin enters into our life when we are born, because the sin nature is a part of our physical body, and remains with us throughout our entire life while living in this world.
We can’t live without our physical body, therefore we cannot escape our relationship with the sin nature, on a physical level.
And the sin nature has such a powerful influence, such that, if we did not have any mental restraint, then we would be totally helpless so far as the sin nature is concerned.
However, God came up with a plan, that gives us a level playing field with the sin nature, and a defense against its influences.
And that defense of course, comes in the form of Jesus Christ, and His work on the cross, and our faith in Him, which identifies us with Him, and therefore protects us against the power of the sin nature.
Without Christ, and doctrine, and faith, we are totally helpless, and in total slavery to the sin nature.
Being born into this world with the sin nature, places us under the Mosaic law, which means we would have to earn our way out of the sin nature, by means of our own effort. And no person is capable of doing that. Thus the law of the sin nature and our total helplessness within that law.
However, Christ went to the cross, and paid the price of sin, thus providing us a way out from under the law of the sin nature.
And faith in Christ, is that way out.
For, by means of His work on the cross, we are set free, through faith, and thus are no longer under the requirement of working our own way out of sin, by our own effort, which we cannot do.
The law of the spirit, identifies the whole concept of Christ and His work of salvation, of our faith, of our study and knowledge of Bible doctrine, of our spiritual life, and the spiritual process in its entirety.
The spiritual process is entirely the design and work of God. Within the spiritual process we merely listen and learn and benefit.
God gets all of the credit. We get no credit, for we do no work within the spiritual life worthy of credit. The spiritual life comes to us in its entirety, and is a gift from God.