"31 Do we, then, nullify (set aside, abolish, etc.) the law by this faith? Not at all! Rather, we uphold the law." (Romans 3:31 NIV)
You say we are not obligated to the law of Moses in any way. Paul says we are. Which part of the law of Moses is Paul saying does not get nullified by faith in Christ?
Of course we know he's not talking about the temple requirements, which do get nullified and set aside by faith, so no need to go there. We're done with that part of the discussion. We have no disagreement there.
"We" don't abolish the law as "we" have no authority to do so.
This was done by the Covenant Maker Himself, on the cross.
4 For He Himself is our peace, who has made both one, and has broken down the middle wall of separation, 15 having abolished in His flesh the enmity, that is, the law of commandments contained in ordinances, so as to create in Himself one new man from the two, thus making peace, 16 and that He might reconcile them both to God in one body through the cross, thereby putting to death the enmity.
Ephesians 2:14-16
having abolished in His flesh the enmity, that is, the law of commandments contained in ordinances...
Since He abolished the law of commandments, not "us" who have faith, which commandments does this scripture say He didn't abolish?
He abolished all the law of Commandments that were added, so that the only ones that remain intact, are the original laws and commandments of the covenant that the law of Moses was added to.
However, the same measure of rule that upholds faith, also upholds the law, which is obedience.
Jesus was the only One Who was obedient to obey all of the law.
Faith in Him and His work of obedience, He accomplished in His life as well as His death on the cross, accredits us with His righteousness that come's from obedience to do all that is written in the law.
Obedience is the common weight of measure that upholds in the scales of Justice.
So by faith in Christ, we achieve the same standard of righteousness as one who obeyed all of the law.
This of course is not obligating us to keep the law of Moses.
This shows those who were being pressured and persecuted, (Jews) to return to keeping the law, after coming to Christ, that they were not being disobedient to God.
JLB