The apostle Paul uses the phase “under law” or “under the law” several times in the New Testament, (three times in Romans, twice in 1 Corinthians, and four times in Galatians).  He uses the phase “under grace” only twice in the whole of the New Testament (Romans 6:14-15).

What do these phrases “under law” and “under grace” mean?  Let’s have a careful look at what these terms mean.

The first mention of “under law” is in Romans 3:19.

Rom 3:19  Now we know that whatever the law says, it says to those who are under the law, that every mouth may be stopped, and all the world may become guilty before God.

The context, which we will look at below, is justification, that is, how we can be made right with God, (how we can become innocent before God).

In Romans 3, Paul uses two Greek words which are similar but tend to be translated with very different looking English words, which can lead to confusion.  The two words are “righteousness” (dikaiosune) and “justified” (dikaioo).  They come from the root word dikaios, meaning innocent, just, right.  In fact, another meaning of dikaiosune is “justification”.

So, we can think of “righteousness” (dikaiosune), “justification” (also dikaiosune), and “justified” (dikaioo) as words concerning the same thing: being made right with God.

Let’s look at the context now.

Rom 3:9  What then? Are we better than they? Not at all. For we have previously charged both Jews and Greeks that they are all under sin.
Rom 3:10  As it is written: “THERE IS NONE RIGHTEOUS [dikaios], NO, NOT ONE;

Paul states that everyone (Jews and Greeks) has sinned and that no one is “righteous” or innocent before God.  Verses 11 to 18 continue the quotes from various Psalms which Paul uses to prove his point.  Now we come to the verse with the phrase “under the law”.

Rom 3:19  Now we know that whatever the law says, it says to those who are under the law, that every mouth may be stopped, and all the world may become guilty before God.

Note that a consequence of being “under the law” is being “guilty before God”.  In other words, those who are under the law, which is all the world, are guilty of breaking the law and are under its condemnation. This is the explanation of the term “under the law”; it means “guilty before God”.

Rom 3:20  Therefore by the deeds of the law no flesh will be justified [dikaioo] in His sight, for by the law is the knowledge of sin.

No one can be justified (made right with God) by keeping the law.  The law shows what sin is, for sin is transgression of the law, 1 John 3:4.

Rom 3:21  But now the righteousness [dikaiosune] of God apart from the law is revealed, being witnessed by the Law and the Prophets,
Rom 3:22  even the righteousness [dikaiosune] of God, through faith in Jesus Christ, to all and on all who believe. For there is no difference;
Rom 3:23  for all have sinned and fall short of the glory of God,
Rom 3:24  being justified [dikaioo] freely by His grace through the redemption that is in Christ Jesus,

Here, “the righteousness of God” is better translated as “the justification of God”.  (Remember, justification is another meaning of dikaiosune). Paul is talking about being made right with God.  Being made right with God, that is being justified, does not come through the law but freely through faith in Jesus Christ by God’s grace (undeserved favour).

So we see that Paul uses the phrase “under the law” in the context of how we are justified.  Moreover, the whole world is “under the law” and guilty before God, verse 19.  But what about Christians?  Are we “under the law”?  Are we guilty before God for having broken the law?  No, we are now “justified (made right with God) freely by His grace”, verse 24.

Paul reiterates this later in his letter, in Romans 6:14-15. 

Rom 6:14  For sin shall not have dominion over you, for you are not under law but under grace.
Rom 6:15  What then? Shall we sin because we are not under law but under grace? Certainly not!

We are not under the law, but we are under grace.  In Romans 3:24, Paul says we are “justified freely by His grace”.  By putting Romans 3:24 together with Romans 6:14-15 we can see that what Paul means when he uses the term “under grace” is that we are “justified freely by His grace”.  We are no longer guilty before God, not by something we do, but as a gift from God by His grace.

Conclusion

We have seen that the terms “under law” and “under grace” concern how we are justified (made right with God).  Romans 3:19 defines “under law” to mean guilty before God for having broken the law, and Romans 3:24 together with Romans 6:14-15  show “under grace” means justified freely by His grace through faith in Jesus Christ.

Under Law means “guilty before God” for having broken the law.

Under grace means “justified freely by His grace” through faith in Jesus Christ.  (We are no longer guilty before God, not by something we do, but as a gift from God by His grace.)