§1. If in the cases mentioned in can. 1448 the judge does not withdraw, a party can lodge an objection against the judge.
§2. The judicial vicar deals with the objection; if the objection is lodged against him, the bishop who presides over the tribunal deals with it.
§3. If the bishop is the judge and the objection is lodged against him, he is to abstain from judging.
§4. If the objection is lodged against the promoter of justice, the defender of the bond, or other officials of the tribunal, the president in a collegiate tribunal or the single judge deals with this exception.
Source: Code of Canon Law (Vatican.va)