I would like to propose the legality of these verses to the likening of a King granting His servants a gift. A gift that does come by oath, and a gift that comes by action. Not just by a promise in our modern understanding.
In the ancient world when a King gave a grant, no one could take it away...especially when it comes to land, i.e inheritance.
Be assured your King has granted Restoration through His Mediator. He has Granted this by Oath and Action. He has granted you an Inheritance if you only accept the means in which He has established it.
Gal 3:15 Brothers, as a man I say it: a covenant, even though it is man’s, yet if it is confirmed, no one sets it aside, or adds to it.
Gal 3:16 But the promises were spoken to Aḇraham, and to his Seed. He does not say, “And to seeds,” as of many, but as of one, “And to your Seed,” who is Messiah.
Gal 3:17 Now this I say, Torah, that came four hundred and thirty years later, does not annul a covenant previously confirmed by Elohim in Messiah, so as to do away with the promise.
Gal 3:18 For if the inheritance is by Torah, it is no longer by promise, but Elohim gave it to Aḇraham through a promise.
Gal 3:19 Why, then, the Torah? It was added because of transgressions, until the Seed should come to whom the promise was made. And it was ordained through messengers in the hand of a mediator.
Gal 3:20 The Mediator, however, is not of one, but Elohim is one.
Gal 3:21 Is the Torah then against the promises of Elohim? Let it not be! For if a law had been given that was able to make alive, truly righteousness would have been by Torah.
Gal 3:22 But the Scripture has shut up all mankind under sin, that the promise by belief in יהושע Messiah might be given to those who believe.
Gal 3:23 But before belief came, we were being guarded under Torah, having been shut up for the belief being about to be revealed.
Gal 3:24 Therefore the Torah became our trainer unto Messiah, in order to be declared right by belief.
Gal 3:25 And after belief has come, we are no longer under a trainer.
Gal 3:26 For you are all sons of Elohim through belief in Messiah יהושע.
Gal 3:27 For as many of you as were immersed into Messiah have put on Messiah.
Gal 3:28 There is not Yehuḏite nor Greek, there is not slave nor free, there is not male and female, for you are all one in Messiah יהושע.
Gal 3:29 And if you are of Messiah, then you are seed of Aḇraham, and heirs according to promise.