This would depend on the context in which it was used.
Romans 3:
9 What then? are we better
than they? No, in no wise: for we have before proved
both Jews and Gentiles, that they
are all under sin;10 As it is written, There is none righteous, no, not one:
19 Now we know that what things soever the law saith,
it saith to them who are under the law: that every mouth may be stopped, and
all the world may become guilty before God.
In this context Paul is saying all people are "Under sin". The law says "the wages of sin is death".
Therefore all man has consciously sinned. They have done what they know is not right according to God. You, me, Abraham, we have all chosen to disobey God. I'm not even going to try and deny or argue with this truth.
So in this context, "under the Law" means, guilty, dead because we broke it.
So now what? How are we freed from this guilt? Well for a time God "ADDED" a temporary Law, that foreshadowed the sacrifice of Jesus, that was to cleanse our sin. And in the fullness of time, God sent His Son who was born into this Levitical System.
4 But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law,
This is a different context. Jesus wasn't guilty of sin. That isn't what Paul is saying. Jesus came to life as a human, as a Jew subject to the Levitical Priesthood system that God called "Carnal commandment" in Hebrews 7. He came in "under" this system to redeem those who were "under sin" both Jew and Gentile.
5 To redeem them that were
under the law, (under sin) that we might receive the adoption of sons.
Two Laws, Law of works, Law of Faith.
22 For it is written, that Abraham had
two sons, the one by a bondmaid, the other by a freewoman.
24 Which things are an allegory:
for these are the two covenants; the
one from the mount Sinai, which gendereth to bondage, which is Agar. (Levitical Priesthood Sacrificial, Ceremonial "works of the Law" for remission of sins.
26 But Jerusalem which is above is free, which is the mother of us all.
The other covenant God made with Abraham.
Gen. 26:
4 And I will make thy seed to multiply as the stars of heaven, and will give unto thy seed all these countries; and in thy seed shall all the nations of the earth be blessed;
5 Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws.
Rom. 3:
27 Where
is boasting then? It is excluded.
By what law? of works? Nay:
but by the law of faith.
2 Laws, one of works that Abraham didn't have, as you pointed out. And the Law of Faith, which Abraham was blessed for keeping.
Of the Law of Works Paul says.
28 Therefore we conclude that a man is justified by faith
without the deeds of the law.
And of the Law of faith that we are judged by:
Rom. 2:
13 (For not the hearers of the law
are just before God, but the doers of the law shall be justified.