§1. By the law itself, diocesan bishops, those who are equivalent to them in law, and coadjutor bishops have a deliberative vote in plenary meetings of a conference of bishops.
§2. Auxiliary bishops and other titular bishops who belong to a conference of bishops have a deliberative or consultative vote according to the prescripts of the statutes of the conference. Nonetheless, only those mentioned in §1 have a deliberative vote in drawing up or changing the statutes.
Source: Code of Canon Law (Vatican.va)