§1. A transfer can be made only by a person who has the right of providing for the office which is lost as well as for the office which is conferred.
§2. If a transfer is made when the officeholder is unwilling, a grave cause is required and the manner of proceeding prescribed by law is to be observed, always without prejudice to the right of proposing contrary arguments.
§3. To take effect a transfer must be communicated in writing.
Source: Code of Canon Law (Vatican.va)