I don’t know if there is any law regulating professional certifications. I inderstand that to practice law your state may require you to be a bar member. Just because you decide to not become a member it does not mean that you don’t have the knowledge or the skills.
If PADI certifies my skills...
Is it legal for a professional Association to require membership to maintain a professional certification?
There are multiple organizations who certify people based on the merit of knowledge and/or skills but require to be a member and maintain the membership to remain certified. Is that legal?