There is no legal forum for CRUZ to bring/begin the legal case. His legal response would be to someone seeking to get him declared ineligible.
There is no forum for him to begin an action to have himself declared eligible.
He is assumed eligible until someone brings an action to have him declared ineligible, and at that time Cruz would fight it.
All I am saying is that the Dems are salivating. IF they get the chance, it will be a spectacle unseen to date.
Incidentally, even McCain got his cronies to go on record saying he was good to go. Of course, there was no big issue there. But he wanted to clarify in advance, at least among his colleagues. It was a considerate thing to do.