In 1 Timothy Paul had just said this. 1 Timothy 1:8-11 NASB.
In Romans 7:13-25 Paul speaks of the law of God in which he delights and the law of sin within his members. It has been said that Paul was speaking of himself or using himself as an example. Some debate whether he was talking about while he was saved or unsaved. Others simply that this is a part of his argument presenting the gospel of Jesus Christ. From verse 25 we can get that, and it seems this is a transition to Romans chapter 8. That is, if we read with chapters and verses (we can know simply that what Paul says next seems to indicate that he has transitioned to the glories of Christ in the gospel. Paul delights in the law. He is opposed to sin. He sees that the Law cannot make him right with God. He sees that Jesus has made us right with God. He speaks of what the Law could not do in the flesh, and what God did sending His own Son in the likeness of sinful flesh and as an offering for sin, that He condemned sin in the flesh, in order that the requirement of the Law might be fulfilled in us who do not walk according to the flesh but according to the Spirit.
I have heard that argument many times that Paul was unsaved when he wrote Romans 7:13-25. Its a dumb argument.
Paul loved the law because the law reveals the righteousness of God and Jesus was the law of God incarnate in human flesh.