Paul is not a slave to the Law of Moses anymore. You need to read on a little further into Romans 8:
find then the principle that evil is present in me, the one who wants to do good. 22 For I joyfully concur with the law of God in the inner man, 23 but I see a different law in the members of my body, waging war against the law of my mind and making me a prisoner of the law of sin which is in my members. 24 Wretched man that I am! Who will set me free from the body of this death? 25 Thanks be to God through Jesus Christ our Lord! So then, on the one hand I myself with my mind am serving the law of God, but on the other, with my flesh the law of sin. Therefore there is now no condemnation for those who are in Christ Jesus. 2 For the law of the Spirit of life [a]in Christ Jesus has set you free from the law of sin and of death.
What do we see in verse 22 and 23: A man (Paul) explaining that while he delights in the Law of Moses, he is still a prisoner to sin. And, again, in verse 25 he talks about serving the Law of God and yet, again, still imprisoned by sin. But verse 2 in chapter 8 declares that something has changed - Paul is no longer engaged in this struggle! He has been set free!
Why is this relevant? It shows that Romans 8:2 is where Paul is now, whereas the stuff at the end of Romans 7 is about where he was in the past. This, of course, does not prove the Law of Moses is retired. But, at the very least it shows that you cannot use statement about "delighting in the Law" from Romans 7 as evidence that the Law is still in force - that stuff is in the past: the Law might still be in force when we arrive at Romans 8.
But then again, it might not.