Health Minister Greg Hunt has launched an extraordinary attack on the ACT, after the United Nations said its legalisation of cannabis may be incompatible with international law.
The UN's International Narcotics Board wrote to Australia's Foreign Minister Marise Payne and Mr Hunt almost a month ago seeking detail about the ACT laws, which allow adults to legally possess up to 50 grams of the drug, and cultivate two plants per person or four plants per household.
"The board has noted with concern recent reports regarding the legislation of cannabis, use and cultivation in small amount in the Australian Capital Territory, effective 31 January 2020," the letter, released on Monday, said.
"The board wishes to recall that the cultivation, production and distribution of cannabis for non-medical purposes is inconsistent with the provisions of the 1961 Convention as amended, in particular article 4(c), which requires state parties to limit the use of narcotic drugs exclusively to medical and scientific purposes.
"The board wishes to reiterate that the legalisation and regulation of cannabis for non-medical use, including in small quantities, would be inconsistent with Australia's international legal obligations."
Mr Hunt said the laws put Australia "very clearly at risk of breaching our international obligations".
He said the ACT government had "blundered in to making laws without any thought" and said the legislation risked Australia's standing with the International Narcotics Board.
"That does have an impact for Tasmania because one of the reasons that we're able to have a strong poppy industry here in Tasmania is because we have the support of the International Narcotics Board," Mr Hunt said.
"The ACT government blundered in to making recreational cannabis changes which are not safe for patients with mental health conditions.
"We know that the evidence is that recreational cannabis can lead to higher rates of schizophrenia. Therefore, it can have huge personal impacts.
"And we also now know that the narcotics board within the United Nations has written to Australia with deep concerns."
Mr Hunt said the ACT's response to his government's concerns had "frankly been inadequate".
"They have been irresponsible and they are blind to the mental health consequences," Mr Hunt said.
"But they also appear to be utterly insensitive to the consequences for Australia, and in particular, for Tasmania."
But ACT Chief Minister Andrew Barr pointed out the United States - which is also a signatory to the convention - had also legalised the drug in some states.
"Canada, Colorado and California have cannabis legalisation laws that are much more expansive than the laws passed by the ACT Legislative Assembly last month," Mr Barr said.
"The International Narcotics Control Board's attention would be better focused on those cannabis legalisation regimes rather than the ACT's reforms.
"It will continue it be illegal to supply and traffic any amount of cannabis in the ACT and the government is not encouraging the personal use of cannabis."
But the United Nations letter makes the legality of the ACT's decriminalisation scheme a little murkier.
"Their law has not done what they think it does, which is provide some kind of defence or out for people who would be possessing cannabis in the ACT. It doesn't do that," Mr Porter said.
"The police enforce laws that are on the books and the Commonwealth law is on the books. The expectation is that police enforce the law. And the law is, as I have been advised and which advice I completely accept, it remains unlawful at Commonwealth law to possess cannabis in the ACT."
The stalemate means it is likely the legality of cannabis will be tested through the courts when the ACT law takes effect at the end of January next year.