Paul answers the above question in Romans 3:19. The law speaks to those who are under the law. It is obvious that the citizens of America are not subject to the laws of Russia. Paul had just quoted extensively from the Law of Moses (3:10-18) and the law said something to the Jews that they did not want to hear. The law in which the Jews boasted (2:17) said to the Jews, “There is none (of you) righteous, no not one” (3:10-18). The Jews were quick to point out the sins of the Gentiles. But they did not want to admit their own guilt before God. But Paul quotes their own law to them “that every mouth may be stopped and all the world may become guilty before God” (3:19). His point is that everybody needs the Savior, Jesus Christ because “all have sinned and come short of the glory of God” (3:23).
In 1 Corinthians 9:21 Paul indicates he was “under law to Christ.” To whom does the law of Christ apply? May I suggest that it applies to Christians? The Jews had no choice. They were Abraham’s descendants, born under the law. We are all volunteers (Psalm 110:3). Shouldn’t we be careful to obey the laws to which we have volunteered rather than condemning those who have not made that choice?