What loophole did God give mankind regarding the death penalty for sin?
God provided a loophole: although every sinner must die because of sin, mankind does not have to die in itself. By believing the gospel, a person can take Christ's death as substitution, and Christ's death takes their place. This is the substitutionary death of Christ.
Les explains that God's first fundamental law was that the day Adam ate of the tree he would surely die, and it is repeated that the soul that sinneth shall surely die. Paul writes that all have sinned and come short of the glory of God, so death is mandated and there is no getting around it. But God gave mankind a loophole: we have to die, but we do not have to die in ourselves. We can take Christ's death as our substitution. If we simply believe the gospel, Christ's death takes our place—the substitutionary death of Christ. He took my place and yours. That is why Paul teaches the old Adam has to be crucified and put to death because he is a sinner, and he that is dead is freed from old Adam.