Article 15 3.

In the cases referred to in paragraphs 1 and 2, Member States shall provide for the controller to inform the data subject, without undue delay, in writing of any refusal or restriction of access and of the reasons for the refusal or the restriction. Such information may be omitted where the provision thereof would undermine a purpose under paragraph 1. Member States shall provide for the controller to inform the data subject of the possibility of lodging a complaint with a supervisory authority or seeking a judicial remedy.