Trying to apply the law of Moses to Gentiles would violate the letter of the law itself since it is addressed only to the Jews at Mt. Sinai and their descendants.
Moses went up to God, and the LORD called to him from the mountain, saying, "Thus you shall say to the house of Jacob and tell the sons of Israel..." (Exodus 19:3)
Exodus 12:38 informs us that a mixed multitude went up from Egypt with the Israelites.
While giving his defense against the false charges against him, Stephen describes Moses as the one who was in the "congregation" [Greek: ekklesia, usually translated as "church"] in the wilderness at Sinai (Acts 7:38). The church was present at Sinai!
Paul tells Gentile believers who were coming to faith in Messiah that they have become part of the "commonwealth" of Israel (Ephesians 2:12).
But there are larger issues that must be considered...
In Romans 3, Paul declares that "both Jews and Greeks are all under sin" (v9) and that
Now we know that whatever the Law says, it speaks to those who are under the Law, so that every mouth may be closed and all the world may become accountable to God; because by the works of the Law no flesh will be justified in His sight; for through the Law comes the knowledge of sin. (Romans 3:19-20)
Why doesn't Paul say that "whatever the Law says, it speaks to the Jews, so that every mouth of the Jews may be closed and all the Jews may become accountable to God"? Because Paul knows that the Law applies to both Jews and Gentiles.
Can anyone honestly say that "do not commit murder" is only for the Jews?
How about "do not commit idolatry", "do not commit adultery", or any other commandment that is not given to the Levitical or Aaronic priesthood?
Paul goes on...
But now apart from the Law the righteousness of God has been manifested, being witnessed by the Law and the Prophets, even the righteousness of God through faith in Jesus Christ for all those who believe; for there is no distinction; for all have sinned and fall short of the glory of God, being justified as a gift by His grace through the redemption which is in Christ Jesus; whom God displayed publicly as a propitiation in His blood through faith. This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed; for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus. (Romans 3:21-26)
There is no distinction between Jew and Greek in our guilt before the Law in the same way that there is no distinction in our salvation by grace through faith in Messiah.
Consider also what Paul writes to the believers in Galatia:
Christ redeemed us from the curse of the Law, having become a curse for us--for it is written, "CURSED IS EVERYONE WHO HANGS ON A TREE"-- in order that in Christ Jesus the blessing of Abraham might come to the Gentiles, so that we would receive the promise of the Spirit through faith. (Galatians 3:13-14)
If the Law does not apply to Gentiles then why does Christ need to redeem Gentiles from the curse of the Law so that the blessings of Abraham might come to us?
Clearly, Paul does not agree with the thought that the law of Moses does not apply to Gentiles.