Yes, they could. But at this point they wouldn't. Many professional organizations offer certification of their profession, which often do nothing but decorate resumes, and sometimes are meaningful indicators of how long someone's been in that profession. But for the most part they are just clubs for the existing players. With time they become entrenched, and sometimes they can convince legislators to give them privileges that others don't have (medical boards are famous for that, and the bar associations are not far behind), but until that happens their certification is meaningless.