Gas regulators must be accessible. The regulator reduces the high pressure of the gas from the mains to a consistent pressure required to use the applianbce safely.
Gas regulators on appliances must be located so that they can be accessed without difficulty and hazard while the appliance is in its installed position. If this standard cannot be met, an installation is considered non-compliant.
AS/NZS 5601.1:2013:Clause 5.11.1.2
A consumer piping gas pressure regulator shall be installed in accordance with all of the following...
d) Readily accessible for maintenance and adjustment.
This information was extracted from: https://esv.vic.gov.au/gas-technical-information-sheets/30-appliance-isolating-valves-and-consumer-piping-regulators/