§1. The interrogation is regularly to be done on the authority of the local ordinary of the converted party. This ordinary must grant the other spouse a period of time to respond if the spouse seeks it, after having been advised, however, that his or her silence will be considered a negative response if the period passes without effect.
§2. Even an interrogation made privately by the converted party is valid and indeed licit if the form prescribed above cannot be observed.
§3. In either case, the fact that the interrogation was done and its outcome must be established legitimately in the external forum.
Source: Code of Canon Law (Vatican.va)