Having Jewish Mothers has little to do with the Law of Return. During the 1st-2nd Commonwealths til 70 CE - Jewish status depended on the inheritance laws of fathers defending land - making sure our children's I.D. was related to a political force under the law. Money/inheritance makes progeny into a certainty. With the loss of the State, only the mother knows her child and hence the identity of the landless Jew depended on mothers not fathers. The Law of Return is a non-religious/racial asylum law of the Modern State of Israel, that insituted thislaw as an answer to Naziism that declared one a Jew til the 10th generation. Hence: our Law of Return is for one who claims to be persecuted because of being a Jew or descended from a Jew to the 2nd or 3rd degree who has not embraced another religion. We Jews in our Kol Nidrei have declared that even one who changed his religion outwardly to escape persecution is still Jewish. That's one up on the Law of Return.
from the article: S.Y. Agnon's relatives: The E. Jerusalem Nashashibis