I often hear people refer to biblical Law in ways which are so obtuse that I wish I could unhear them. That is a gift, which God has, so far, not seen fit to grant me.
On one hand, I have Catholics and Mormons who deny justification by grace through faith alone by insisting that the works which are excluded by Paul refer not to all works, but rather only those involving the ceremonial law of Moses. "For by works of the law no human being will be justified in His sight, since through the law comes knowledge of sin" (Romans 3:20). And it is certainly true that the Old Testament sacrifices were according to Law.
On the opposite extreme, I am frequently confronted by dispensationalists who parrot "you are not under law but under grace" (Romans 6:14) over and over if I say anything favorable about God's Law.
Of course, both views are unbiblical. One is an effort to sustain a works righteousness by which the believer cooperates in his own justification. The other is bald-faced antinomianism, a false view that the free grace of God means that a person can be a true believer no matter how he lives. Unbiblical and false!
The error of both sides described above is the result of equivocation. They take one particular meaning of the word "law" and use it in a different context. It is as if I said, "John is from Jamaica," and you take it to mean the island of Jamaica, when I actually meant that he is from the city of Jamaica, New York.
The word "law ("torah" in Hebrew or "nomos" in Greek) has eight different meanings in Scripture:
1) law of nature (Rom. 2:14-15)2) the corruption of human nature (Rom. 7:23)
3) the entire word of God (Ps. 19:7-8)
4) the books of Moses (Luke 24:44)
5) the gospel (Rom. 3:27, Isa. 2:3)
6) the civil laws (John 19:7)
7) the ceremonial laws (Heb. 10:1)
8) moral law, especially the Ten Commandments (Matt. 22:36-38)
When Paul tells us that justification by faith necessarily excludes any works of the Law, he cannot be referring to the works of the Mosaic ceremonies, i. e., number 7 above, because very few of them were performed by the individual believer; it was only the priests that performed, for example, the sacrifices. And, since those ceremonies ended with the destruction of the Temple in 70AD, it would be a tautology to say that we are not justified by those same ceremonies.
Also, when Paul says that "we are under grace, not under law," he cannot mean that we have no obligation to the moral Law of God (number 8 above), because those two things are directed to different ends. Grace is the application of the merits of Christ to the elect. it is how we are justified. The moral Law, however, as that name implies, is a matter of how to live. One cannot be brought to life by a rule of life. That can only be done by grace. Once grace has brought new life, the Law then tells the believer how to live that life. It's like a car loan. That loan is the means for attaining a new car. However, the car loan is not the means for driving the car. It takes a manual to do that. The loan is the grace, the manual is the Law. They are not in opposition, as long as neither is used in place of the other.
We see this described vividly in Ezekiel 36:26-27: "I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh. And I will put My Spirit within you, and cause you to walk in My statutes and be careful to obey My rules. You shall dwell in the land that I gave to your fathers, and you shall be My people, and I will be your God." The new heart, a biblical image of justification, is God's gracious act, in which the new believer makes no contribution. That is grace. The effect of this new heart is that he is now enabled to obey God's Law (not perfectly, but progressively in this life). That is sanctification.