Recital 138

While this Directive specifies a minimum set of powers competent authorities should have, those powers are to be exercised within a complete system of national law which guarantees the respect for fundamental rights, including the right to privacy. For the exercise of those powers, which may amount to serious interferences with the right to respect private and family life, home and communications, Member States should have in place adequate and effective safeguards against any abuse, for instance, where appropriate prior authorisation from the judicial authorities of a Member State concerned. Member States should allow the possibility for competent authorities to exercise such intrusive powers to the extent necessary for the proper investigation of serious cases where there are no equivalent means for effectively achieving the same result.