What are the grounds for there being no condemnation in Christ?
The grounds are that believers have been justified by faith, not by fleshly effort. Christ died, was buried, and rose again, and all of this was accomplished as God's act, with nothing contributed by human energy. Because it was entirely God's work, the resulting security rests on His finished work, not on human striving.
Les explains that chapter 8 follows the struggle described in the previous chapters, where the problem is wanting to do right but not doing it, and doing what one should not do. The "therefore" of no condemnation wraps up everything learned in the previous seven chapters. Les teaches that many who claim to be Christians cannot accept this security; they insist you must work, strive, and be careful or you will lose it. But that leaves them in perpetual insecurity, because no one has the wherewithal to hang on by themselves. The grounds are that we have been justified by faith, because Christ died and was buried and rose from the dead, because all of this was accomplished as an act of God in which we had nothing of our own energy. Nothing in it could be done in the flesh; it was all the work of God. Our justification is by faith, which is invisible and not something you work at.