declaring a legislative agency rules invalid

A state legislature passed enabling legislation, estabishing a board to regulate the profession of pharmacy, as well as business establishments engaged in pharmacy. The law gives the agency guidance in stablishing licensing requirements and specifically states that no person may be licensed as a phamacist unless he hass attained the age of twent-one years and has a degree from an accredited school of pharmacy. The agency thinks that these requirements are not wise and thus enacts a rule allowing anyone over the age of 16 to become a licensed as a pharmacist and additonally the rule provides that a person does not have to have a degree in pharmacy, but rather, any college degree will qualify the applicant. The pharmacy association, a professional group of licensed pharmacists, brings an action seeking to have the rule declared invalid. That would be the standing to sue?