What is the difference between the incorporation system and the transformation system?

Answer 1

Under the doctrine of incorporation, a rule of international law becomes part of national law without the need for express adoption by the local courts or legislature. As a result the domestic courts have to apply a certain rule of international law as long as they there is no explicit contradicting piece of law or judgement.

Differently from the latter theory, the transformation doctrine stipulates that rules of international law do not became part of national law until they have been expressly adopted by the state. To become binding on domestic authorities, the international law must transformed into national law through the various mechanisms for the national implementation of international rules freely decided upon by each sovereign State.