The 1920s are interesting years for drug use in Australia because that is when legislation began to be broadened to control the recreational use of drugs. Prior to that legislation had targeted smoking opium, largely because it was considered a vice restricted to chinese immigrants, while permitting the import of opium derivatives (laudanum, morphine, heroin) for medicinal use. The legislative control was by having them listed as "prescribed substances" under the State "Poisons Act". The Phryne Fisher books are mostly set in various locations in the Australian State of Victoria. The Victorian Poisons Act 1925 lists Opium and opium pipes as prescribed substances, most Opium derivatives and Cocaine as requiring a doctor's prescription but does not list Indian Hemp (Cannabis). The Victorian Poisons Act 1927 does list Indian Hemp (the dried flowering or fruiting tops of Cannabis Sativa L. "by whatever name such tops are called") after Federal legislation banned it in 1926.

So as to the respectability of the character, cannabis use was legal until 1926. It was available to buy in cigarette form (Cigares de Joy) and there hadn't been any social pressure against it as it didn't feature in any of the newspaper drug scares of the 1920s. Hemp had been grown in Australia since the First Fleet but there aren't any reports of it being used widely as a recreational drug.

On the other hand cocaine was used widely as a recreational drug until the 1920s and was identified with the demi-monde like artists and musicians although it was also heavily prescribed for middle aged women for menstrual pain and depression so despite changing legislation there was widespread social acceptance of drugs for personal use. It was largely considered a private matter unless it intruded into the public sphere.