ex officioex of·fi·ci·o /ˌeks əˈfɪʃiəʊ-oʊ/ adjectiveadj an ex officio member of a group or organization is a member because of their senior rank or position, not because they have been chosen by othersThe National Assembly is composed of 228 members: 168 directly elected, 25 ex officio, and 35 indirectly elected.
—ex officio adverbadvThe delegates don’t have to be elected, they can go to these conventions ex officio by virtue of being union officers.