I know they have a lawyer-drafted justification on file with the DOJ, but to the point of “courts permission” has that actually ever been tested in a real court (not FISA)? And if so is the decision public?
It's unlikely that a corpse files suit to protect their constitutional rights, of which no one is aware were violated in the first place.
However unlikely, it is possible. Many such cases where the estate of the dead or their families have brought suit against the US government.