It doesn't matter if you observe the law of Moses, the commandment of Christ, or make a list of your own combining all of these.
It is still law that you have set to observe and to do.
Paul said that "grace is no more of works."
And in context, Paul was talking to the Jew who needed to be saved. Paul was talking about the "Law of Moses" and "Law Alone Salvationism" in Romans 11:6. You are ripping verses out of their context and seeing what you want to see.
The context is Israel who needed God's grace.
"I say then, Hath God cast away his people? God forbid. For I also am an Israelite,..." (Romans 11:1).
"What then? Israel hath not obtained that which he seeketh for; but the election hath obtained it, and the rest were blinded" (Romans 11:7).
We are to stand by faith, and continue in God's goodness, otherwise we can be cut off.
"Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear: For if God spared not the natural branches,
take heed lest he also spare not thee. Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in
his goodness: otherwise thou also shalt be cut off." (Romans 11:20-22).
Continuing in the faith is not only believing those words on God's grace in NT Scripture, but it is believing by faith those words in NT Scripture on obeying the Lord, as well. Hebrews 5:9 says God is the author of eternal salvation to all who OBEY Him. You want salvation to be all about a belief alone in Jesus, but it doesn't work like that. We have to also obey the Lord.
For Jesus says,
"And why call ye me, Lord, Lord, and do not the things which I say?" (Luke 6:46).
Side Note:
Israel made salvation all about the Law Alone Salvationism (with little to no grace). Israel did not accept the Messiah Jesus Christ. Israel looks to the Tanakh (i.e. the Old Testament Scriptures) as their sole form of salvation and they do not accept the New Testament Scriptures. They look to the 613 laws of Moses as a means of salvation. Hence, this is why Paul said what he did in Romans 11:6. Paul was warning the brethren at Rome about how not to think like the Israelite and be justified by the Law of Moses with the Torah or the five books of Moses. This would essentially be Law Alone Salvationism. Hence, from this perspective it is true. If one is trying to be saved by Law Alone, it surely is no more grace or faith in Christ. Paul was warning the Roman brethren not to be like the Jews and go back to the Old Law as a means of salvation like them. This is the context of what Paul was referring to and he was not referring to how we need to obey God after we are saved by God's grace. For Titus 2:11-12 says that God's grace teaches us to deny ungodliness, and that we should live righteously and godly in this present world.