Specifier usually could only be liable if the railing was less than any code requirement when designed/constructed. Can't hold a specifier liable for future code changes. Also, if it was code deficient, what about the Building Inspector that issued the C.O.?
Were there any legal requirements to bring deficiencies up to code? I am not sure about railings and such but for electrical systems, usually only have to bring deficiencies up to current code if expanding.