Lo HaBayshan Lomed!
Lets say a man had a daughter and no sons (when the din was in effect). We would not allow his daughter to marry out of the shevet.
If the man had sons, the daughter can marry who she wants (the mitzva only affects a “Bas Yoreshes”, which she at the weeding is not). Then if the son subsequently dies, she gets the yerusha (when her father dies), but has done no Issur (there was no “Bas Yoreshes” who AT THE TIME OF THE CHASUNA married outside the shevet). Therefore the Nachala will transfer if she dies, and the husband is Yoresh.
The system is not meant to be foolproof, only to remove most cases of land transfer.