(a) the act or omission that would but for this provision have constituted the offence or an element of the offence was authorised by or under the Act or these Regulations; or
(b) in any other case—
(i) the act or omission that would but for this provision have constituted the offence or an element of the offence occurred during the conduct of an activity that was, apart from the Act or these Regulations, lawful; and
(ii) in conducting the activity, the person was complying with the general environmental duty.