Rates of cannabis use in Canberra have remained stable in the nearly five years since possession of the drug was decriminalised, an ACT government review has found.
But the conflict with Commonwealth laws on drug possession is continuing to be a challenge for officers.
The ACT Health review found charges laid for cannabis offences have declined to very low levels and there had been no increases in charges laid for trafficking or cultivation offences since the laws came into place in early 2020.
Data showed there were 200 charges related to cannabis offences in 2019 but this dropped to fewer than 20 in 2023.
"These data indicate that the legislative change had the intended effect of reducing the criminal justice system involvement of people who possess and cultivate small amounts of cannabis for person use," the report said.
A review of the laws, required under legislation, found no changes were needed to the ACT at this stage. The laws came into place in 2020 and allow ACT residents over 18 to grow cannabis at home with a limit of two plants a person or four in a household.
People are allowed to be in possession of 50 grams of dried cannabis and 150 grams of wet cannabis. The ACT decriminalised the possession of small amounts of illicit drugs last year.
Police told the review the laws had led to less administrative burden but the conflict with Commonwealth law did pose an issue.
"The concerns we've raised regarding the legal ambiguity is probably the most significant challenges that we would continue to note as being an issue for members," police told the review.
"To a large extent ... we have been able to adopt internal governance to encourage our police to defer to using ACT law.
"While it's been decriminalised in the ACT, under Commonwealth law it's still an offence ... due to the independent Office of the Constable, officers still can't be directed whether or not to utilise particular offences. So that tension still does exist for our members."
Under Commonwealth law the possession and cultivation of any amount of cannabis is illegal and a person can face up to two years in prison.
But data has shown there have been fewer than five charges under Commonwealth law for drug possession over the past five years.
Police were also concerned drug dealers had been using their knowledge of the laws to get away with trafficking. Police pointed to an example of a report they received that a man had been selling cannabis to children. He denied selling cannabis and successfully argued the amount was within the possession limit.
"I think criminals are becoming more acute to what the laws are. That makes it more challenging for our members to be able to engage here," police told the review.
The review found there did not appear to be any change in the number of cannabis-related presentations to hospitals.
The review, required under the legislation, had interviews with stakeholders including police, health authorities, the Alcohol, Tobacco and Other Drug Association and the Canberra Alliance for Harm Minimisation and Advocacy.
The Canberra Alliance for Harm Minimisation and Advocacy expressed concern with the quantitative limits under the act. The alliance's executive director Chris Gough said the 50 gram limit for dry cannabis and the 150g limit for wet cannabis did not reflect the seasonality of growing cannabis.
"The way the plant works, it's actually quite difficult for people to stay within those 150 grams wet, 50 grams dry, two plants [limits]. Because what tends to happen is that the plant will just go from not flowering, and then... the plant will just flower in its entirety and then will die after that because it's an annual," he said.
Mr Gough said this meant people could not just keep taking 50 grams off a plant in one year and he said this meant people were still forced to turn to the black market to get their supply.
He suggested this could be tackled by allowing a growers club where people could share supply or by exploring a government-regulated cannabis market.
The review ultimately found the laws were operating as intended with limited unintended consequences and no changes were recommended.
Population Health Minister Emma Davidson said, in a written ministerial statement, the review had shown the laws were working well.
"The review, despite some of the issues raised, has overwhelmingly illustrated the positive impact decriminalising the personal use of cannabis has had on our community, the health system and the alcohol and other drug treatment and support sector," she said.
