I think from the Romans 3:31 verse that 'uphold' means the opposite of 'nullify':
"31 Do we, then, nullify the law by this faith? Not at all! Rather, we uphold the law." (Romans 3:31 NIV)
Nullify means to make of 'no effect', 'inapplicable' perhaps? From the passage, 'uphold' would, therefore, mean the opposite.
Here is what Wuest's Word Studies of the Greek says about Galatians 4:5, "the word law is not preceded by the definite article, hence law in general is referred to here" (Volume 1, p. 115)." The definite article is "the".
Galatians 4:4-5 KJV
Gal 4:4 But when the fulness of the time was come, God sent forth his Son, made of a woman, made under
the law,
Gal 4:5 To redeem them that were under
the law, that we might receive the adoption of sons.
Young's Literal Translation
4 and when the fulness of time did come, God sent forth His Son, come of a woman, come under law,
5 that those under law he may redeem, that the adoption of sons we may receive;
You can look at the Greek here....
http://www.scripture4all.org/OnlineInterlinear/NTpdf/rom3.pdf
Well we know that Paul clearly said that Gentiles were not under the Law of Moses, Moses being the Mediator of that Law. So if verse 4 is talking about the Law of Moses than one of two things most be true, I think.
1. Gentiles were not under the Law of Moses until they became believers and then they are or
2. verse 5 does not include Gentiles as being redeemed and adopted as sons and most of the NT was not written for Gentiles at all.
So how we interrupt verse 4 is essential in understanding verse 5 and reconciling verse 4 with Paul's teaching about Gentiles and the Law of Moses.
So when was the seed of woman first mentioned, in Genesis. Was law in effect in Genesis? The minute that Adam sinned the law of "sin and death" went into effect.
Romans 3:21 KJV
21 But now the righteousness of God without
the law is manifested, being witnessed by
the law and the prophets;
Young's Literal Translation
21 And now apart from law hath the righteousness of God been manifested, testified to by
the law and the prophets,
In the Greek there isn't the definite article "the" but the second use there is. By the way I think the second use "the law" is the whole law (Torah). Because beginning in Genesis we see the witness to Christ.
Romans 3:31 KJV
31 Do we then make void
the law through faith? God forbid: yea, we establish
the law.
Young's Literal Translation
31 Law then do we make useless through the faith? let it not be! yea, we do establish law.
The Greek as Young has translated and in the interlinear makes sense of the whole teachings. Paul was a brilliant man, I don't believe that the use of the definite article was by chance and those hearing it in the Greek would have understood what he was saying. I think that Romans 3:21 where there is no definite article and then there is, where it clearly states "the law and the prophets", shows Paul to be making a differentiation.
I'm not a good writer but I hope this is somewhat clear as to what I am seeing.
Blessings