(4) Where the use of a road or pathway is prohibited or a cordon is set up around an area, place or premises under this section, a person who, without the permission, whether oral or written, of a police officer, after being challenged commits an offence if he or she —
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(a) enters or departs from that area, place or premises or attempts to enter or depart from that area, place or premises;
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(b) removes any sign, instrument light or other object designed to inform another person of the prohibition or cordoned area.