How does achieving accreditation for a certification or certificate program provide legal defensibility for the program?
1) It means you developed your program in conformance to an industry-recognized standard (ASTM E2659, ISO 17024 or NCCA, as examples). In other words, you didn't just make up your own quality rules.
2) By achieving accreditation, you have third-party objective confirmation that you conformed with the standard (versus first-party verification where you say you followed the standard), second-party (a consultant or vendor says you followed the standard - they are separate but not independent since they liked worked with you to create or implement the program) vs third-party (the accreditor - such as ANAB or NCCA - who provides a formal, independent verification).
Caveat: I am not a lawyer and don't even pretend to be one on TV.