The Greens and the Labor executive have already flagged that they will make amendments to the private members bill from Labor backbencher Michael Pettersson when it returns to the ACT Legislative Assembly for debate next week.

However, the Assembly's new standing order requires all amendments to bills to go through the parliament's scrutiny committee first.

Under the old rules, only government amendments had to be dissected by the committee, which gets legal advice on the changes proposed then publishes a report for the Assembly to consider.

Chief Minister Andrew Barr said it was likely debate on Mr Pettersson's bill would not be concluded for several months, "possibly not even by mid year at this point".

"The new standing orders of the Assembly require all amendments to go through a scrutiny process so if there’s any contention around a piece of legislation in the Assembly it will take three sitting periods effectively for it to be resolved, so we intend to have a measured and detailed debate both on the principle of the legislation and any subsequent amendments," Mr Barr said.

"This will not be progressing through the Assembly in this sitting fortnight and it may in fact be the middle of the year before debate concludes on all of the amendments that will be brought forward but I welcome engagement on the issue, I think it is long overdue this debate and I’m hopeful the Assembly will be able to conduct itself in a mature and exemplary way in considering both the in principle part of the debate and also amendments."

The standing orders were changed upon recommendation from ACT Parliamentary Counsel Mary Toohey, who said scrutiny should be extended to all legislative amendments, regardless of their origin, "as a matter of principle".

While standing orders can be suspended by a majority of the Assembly, Mr Barr said this was an "abuse" of the process and having that extra scrutiny meant better legislation.

The Liberals will also try and refer Mr Pettersson's bill to the Assembly's standing committee on health, which would delay the bill further but is unlikely to happen as both Labor and the Greens support the legislation in-principle.

It's still unclear what changes the Labor executive are seeking on the legislation, but Mr Barr said his ministers would bring forward amendments "across multiple portfolios".

It comes after the Greens signalled they would move to increase the amount of cannabis people can possess for medicinal use, as well as allowing people to grow hydroponic cannabis in their homes.

The bill as drafted allows people to cultivate up to four cannabis plants each but they cannot use any artificial lights.

The minor party also wants to create an advisory council to give the government expert advice on the issue and introduce new objectives for drugs of dependence laws to enshrine a harm minimisation approach.

And while the Liberals oppose the bill outright, Mr Barr said their legal affairs spokesman Jeremy Hanson had raised some issues in an opinion piece for The Canberra Times that warranted further examination through the details stage of the bill.

Other issues Mr Hanson raised though pointed to "philosophical differences in relation to harm minimisation versus a 'just say no' approach", Mr Barr said.

"I think we are going to get a reform path here, we’re going to pursue that, but the fine detail of the legislation will take many months to work through," Mr Barr said.

Mr Pettersson also said he was aware of amendments to his legislation but was yet to see detail.

"I encourage all MLAs to engage with this legislation, which is so important so many members of the community," Mr Pettersson said.

Asked whether his bill should be examined through a committee, Mr Pettersson said he was unable to take the suggestion seriously given the Liberals refusal to consider supporting the legislation.