Dear SnuP,
I agree that they needed to repent and live by faith, but it is by grace that they will do that. Romans 2:4 tells us: "Do you think so little of the riches of His kindness, forbearance, and patience, not realizing that it is God's kindness that is leading you to repentance?"
There is a difference between being under the law and living like you are under the law. Paul wasn't telling them the were under law but living like it. Look at the last few verses of chapter 4. Verse 31 tells us: "So then, brothers, we are not children of the slave woman but of the free woman."
You become a child of the 'free woman' by having faith in the promise, by being born again. Who are you? You are a child of the free woman. That is who you are and you cannot change that by actions [works] because you have been born from above by the Spirit of God.
But you can seek to live like you are still enslaved [a child of the slave woman]. He is not talking about whether one is saved or not but about the BENEFITS of the freedom we have in Christ. When we choose to submit to the law, the benefits we have by living by faith go bye bye. That is what it means when it says that if we allow ourselves to be circumcised, Christ will be of no benefit to us.
Verse 13 tells us that we have been called to freedom. We are are called to because we are free in Christ, so the call is for us to live in that freedom, both by realizing we have it [we are not under law] and by not using the freedom to sin. Verse 18 tells us that if we are being led by the Spirit, we are not under the law.
Romans 8 further clarifies this: 9-14 However you are not under the control of the flesh but under the control of the spirit, since God's spirit lives in you. Whoever doesn't have the Spirit of Christ doesn't belong to Him. If Christ is in you, your bodies are dead because of sin, but the Spirit is life because of righteousness. And if the Spirit of the one who raised Christ from the dead lives in you, then the one who raised Christ from the dead will also make your mortal bodies alive by His Spirit who lives in you. So then brothers, we don't owe it to the flesh to live the way the flesh wants us to live. If you live by the flesh, you are going to die, but if by the Spirit you continually put to death the activities of the body, you will live. For all who are led by the God's Spirit are God's children."
If we have the Spirit, we are God's children and will be led by Him. We will sometimes stumble, sin and lose focus, but because of WHO we are [children of God because we have the Spirit] we will be led on towards God.
It is because of WHO we ARE[children of the free woman] that we can never be children of the slave woman [WHO we WERE] EVEN IF we try and live like it.
So who brings back His children who are trying to live under law [slavery] and not grace? God does. It is by His kindness that we are led to repentance.
love in Him,
mike