Heb 7:1-7 For this Melchizedek, king of Salem, priest of the Most High God, met Abraham returning from the slaughter of the kings and blessed him, and to him Abraham apportioned a tenth part of everything. He is first, by translation of his name, king of righteousness, and then he is also king of Salem, that is, king of peace. He is without father or mother or genealogy, having neither beginning of days nor end of life, but resembling the Son of God he continues a priest forever. See how great this man was to whom Abraham the patriarch gave a tenth of the spoils! And those descendants of Levi who receive the priestly office have a commandment in the law to take tithes from the people, that is, from their brothers, though these also are descended from Abraham. But this man who does not have his descent from them received tithes from Abraham and blessed him who had the promises. It is beyond dispute that the inferior is blessed by the superior.
Heb 7:12-19 For when there is a change in the priesthood, there is necessarily a change in the law as well. For the one of whom these things are spoken belonged to another tribe, from which no one has ever served at the altar. For it is evident that our Lord was descended from Judah, and in connection with that tribe Moses said nothing about priests. This becomes even more evident when another priest arises in the likeness of Melchizedek, who has become a priest, not on the basis of a legal requirement concerning bodily descent, but by the power of an indestructible life. For it is witnessed of him, "You are a priest forever, after the order of Melchizedek." on the one hand, a former commandment is set aside because of its weakness and uselessness (for the law made nothing perfect); but on the other hand, a better hope is introduced, through which we draw near to God.
Jesus was appointed as the eternal High Priest before God on our behalf even though he did not descend from Levitical tribe but from Judah. His high priesthood is therefore not a continuation of Levitical priesthood--in fact, His is in the order of Melchizedek, long before the Law came into being (some 400 years later). Which means that those who are "in Christ" is not obligated to Mosaic Law. The Levitical priesthood was part of the Law of Moses (as contained in the book of Leviticus). So, Jesus' high-priestly pre-dated Moses because it did not originated from Aaron but from Melchizedek.
So, when Paul says that Christ is the "end of the Law" (Rom. 10:4), he meant the end of obligations to the Mosaic Law, not the end of moral and spiritual law. In place of the Mosaic Law, Jesus the new High priest instituted the the Law of the Spirit of life, which is an inward moral and spiritual character formed through obedience to Christ, not to a set of rules. The problem with legalism is not presence of rules and regulations but to think that by keeping the rules (even spiritual ones) we will become Christ-like.
So Paul writes in Romans 8:1-4
- "Therefore, there is now no condemnation for those who are in Christ Jesus, because through Christ Jesus the law of the Spirit of life set me free from the law of sin and death (Mosaic Law). For what the (Moses') law was powerless to do in that it was weakened by the sinful nature, God did by sending his own Son in the likeness of sinful man to be a sin offering. And so he condemned sin in sinful man, in order that the righteous requirements of the law might be fully met in us, who do not live according to the sinful nature but according to the Spirit.
So, Paul is in fact saying that when we live "according to the Spirit" (i.e. obey His leading), the righteous requirements of the law "might be fully met in us." Now we are righteous not by obeying rules (moral or spiritual ones) but by obeying the Spirit.
Be that as it may, it doesn't mean Christians should or can ignore all rules and regulations. We ought to observe civil laws and rules for sake of societal order and peace but our eternal salvation is not based on our ability to keep these rules and regulations like the traffic laws, organizational rules and regulations, social etiquette or even religious practices e.g. head-covering in some churches, bowing at the altar, etc). So Paul says in 1 Corinthians 9:20-21, "To the Jews I became as a Jew, in order to win Jews. To those under the law I became as one under the law (though not being myself under the law) that I might win those under the law." He even got Timothy circumcised in order not to offend the Jews in the areas they were going (Acts 16:3).
Those who claim that grace gives them freedom to do as they please have confused liberty (freedom to please God) with license (freedom to please myself).
Father, thank You that You have granted us freedom in Christ from obligations to the Law of Moses, so that we can be free to please You, not ourselves. Amen.