Romans 3.27 Where is boasting then? It is excluded. By what law? of works? Nay: but by the law of faith.
Romans 8.2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
A law describes something that guarantees results. For example, the law of gravity says that what goes up, must come down. You throw a ball up in the air, and as sure as the sun rises in the east (a law of nature), that ball is coming down.
God has established laws in the realm of The Spirit, just as He has established laws in the realm of creation. In Christ Jesus, we are given the Spirit of life. That life in Christ is given unto us through the law of faith. When you by exercise of the law of faith trust in Jesus Christ as Lord and Redeemer, God supernaturally places within you the Spirit of life. That Spirit of life in Christ supersedes the law of sin and death that once governed how we lived and our old ways of thinking.
Whenever a child of God places their faith and trust in God’s promises or chooses to obey God’s Word in spite of outward circumstances or emotions, that law of faith activates the law of the Spirit of life in Christ Jesus. This is not magic. This law of faith and life in Christ Jesus doesn’t make “bad things” disappear into thin air. A simple reading of Romans 8 proves that. It means that the supernatural life in The Spirit prevails over the natural laws of this world.
When Jesus told the disciples, Have faith in God, He was revealing to them a way of living that is not of this world, and stronger and greater than the mountains we face in our lives on earth.