how is it possible for a "Grandfathered"deffect not to be libel in a civil case?

Answer 1

You need to be more specific. An example where grandfathering is used is in building materials. Lets say you bought a house built in 1967. The sliding glass patio back then did not use tempered glass. Lets say your neighbor gets hurt slamming the door and the glass breaks off in big chunks, and he tried to sue you. You are protected because you bought the house with pre-existing building materials. Now, had you previously broken the glass and used replacement glass that was not tempered, you would be liable. ***The glass company would not make glass for a patio that is not tempered because it is against the law.