idea how such a thing would actually be ruled.
I don't think Luke would win the argument that portions of "his" DNA were used in an unlawful search. It's true that he has some sections of his genome that are identical to Leia's, but it is still her DNA that was used, not his. All humans share something like 99.9% of their genome with each other. That doesn't mean that 99.9% of the genome in some guy down the street is mine. Just that it's shared with me.