An approval under s 6 of the Fluoridation of Public Water Supplies Act 1957 (NSW) does not impose an obligation on a water supply authority to fluoridate; it merely empowers the authority to do so. A direction under s 6A, by contrast, imposes a mandatory obligation. Erroneous legal advice received by a decision-maker, even if shown to be wrong, does not vitiate the decision unless the advice is shown to have been causative of the exercise of power or duty miscarrying in law. Where a statutory duty (such as s 111 of the EPA Act) involves an objective standard that has been adequately discharged, a subjective misapprehension by the decision-maker about the legal framework does not constitute a constructive failure to exercise jurisdiction.
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