1. With respect to national requirements which may be imposed pursuant to Articles 16 or 17, the Member State where the service is provided is responsible for the supervision of the activity of the provider in its territory. In conformity with Community law, the Member State where the service is provided:

(a) shall take all measures necessary to ensure the provider complies with those requirements as regards the access to and the exercise of the activity;

(b) shall carry out the checks, inspections and investigations necessary to supervise the service provided.

2. With respect to requirements other than those referred to in paragraph 1, where a provider moves temporarily to another Member State in order to provide a service without being established there, the competent authorities of that Member State shall participate in the supervision of the provider in accordance with paragraphs 3 and 4.