189In addition, a decision authorising the real-time collection of traffic and location data must be based on objective criteria provided for in the national legislation. In particular, that legislation must define, in accordance with the case-law cited in paragraph 176 of the present judgment, the circumstances and conditions under which such collection may be authorised and must provide that, as was pointed out in the previous paragraph, only persons with a link to the objective of preventing terrorism may be subject to such collection. In addition, a decision authorising the real-time collection of traffic and location data must be based on objective and non-discriminatory criteria provided for in national legislation. In order to ensure, in practice, that those conditions are observed, it is essential that the implementation of the measure authorising real-time collection be subject to a prior review carried out either by a court or by an independent administrative body whose decision is binding, with that court or body having to satisfy itself, inter alia, that such real-time collection is authorised only within the limits of what is strictly necessary (see, to that effect, judgment of 21 December 2016, Tele2, C‑203/15 and C‑698/15, EU:C:2016:970, paragraph 120). In cases of duly justified urgency, the review must take place within a short time.
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