§1. No one can be brought to trial in first instance except before an ecclesiastical judge who is competent by reason of one of the titles determined in cann. 1408-1414.
§2. The incompetence of a judge supported by none of these titles is called relative.
§3. The petitioner follows the forum of the respondent. If the respondent has more than one forum, the choice of forum is granted to the petitioner.
Source: Code of Canon Law (Vatican.va)