http://www.legislation.gov.uk/ukpga/2016/25/section/91/enactedInvestigatory Powers Act 2016enKing's Printer of Acts of Parliament2019-08-16 Part 4 91 1 In deciding whether to approve a decision to vary a retention notice as mentioned in section 90(10)(a), or to give a notice under section 90(10)(b) confirming the effect of a retention notice, the Investigatory Powers Commissioner must review the Secretary of State’s conclusions as to whether the requirement to be imposed by the notice as varied or confirmed to retain relevant communications data is necessary and proportionate for one or more of the purposes falling within paragraphs (a) to (j) of section 61(7). 2 In doing so, the Investigatory Powers Commissioner must— a apply the same principles as would be applied by a court on an application for judicial review, and b consider the matters referred to in subsection (1) with a sufficient degree of care as to ensure that the Investigatory Powers Commissioner complies with the duties imposed by section 2 (general duties in relation to privacy). 3 Where the Investigatory Powers Commissioner refuses to approve a decision to vary a retention notice as mentioned in section 90(10)(a), or to give a notice under section 90(10)(b) confirming the effect of a retention notice, the Investigatory Powers Commissioner must give the Secretary of State written reasons for the refusal.