What is the big difference in living under the Law of the Spirit?
The big difference is that under the Law of the Spirit, the Spirit indwells the believer. The Mosaic Law had no power to help anyone keep it and could only condemn. Under the Spirit, His indwelling presence marks the new covenant work in contrast to the faulty first covenant.
Les teaches from Hebrews 8 that the first covenant, the Law of Moses, was faulty from mankind’s perspective because man could not keep it. It was perfect from God’s perspective, but not from mankind’s. The Law had no power to help mankind keep the Law, and it had no power to keep a man from stealing, committing adultery, and similar sins. All it could do was condemn him. Then, coming back to Romans chapter 8, when considering living under the Law of the Spirit, the big difference is that the Spirit indwells us, as was seen in 1 Corinthians 3 and 6.