"Cardcarrying" is a commonly-used term to describe someone who is an active member of a specific group or organization. Conversely, antonyms for "cardcarrying" would describe individuals who have no affiliations or who are not active members of particular groups.
Some antonyms for "cardcarrying" include independent, unaffiliated, detached, impartial, and neutral. These terms imply an individual's lack of association with any specific entity, group, or ideology.
Another set of antonyms for "cardcarrying" would be terms describing someone who is not authorized or recognized by the group in question, such as unapproved, unauthorized, unendorsed, or unaccredited.