Police warn "legalising" recreational cannabis in Canberra would leave them with no choice but to enforce federal criminal laws, meaning more people would end up imprisoned over the drug as a result.

Key points: Police say they would have to enforce criminal laws if ACT laws were removed

Police say they would have to enforce criminal laws if ACT laws were removed But the drug sector's peak body says only a quarter of cannabis use arrests led to a fine last year

But the drug sector's peak body says only a quarter of cannabis use arrests led to a fine last year The ACT's chief police officer warned legalising cannabis could help fund more organised crime

The ACT Government has proposed legalising cannabis for personal use, allowing the cultivation of two plants and possession of up to 50g of the drug.

Police currently have the discretion to give users a simple fine under ACT law, or charge them with up to two years' prison under Commonwealth law.

But, in a submission to an inquiry, Chief Police Officer Ray Johnson said even if local laws were removed, officers would still have an obligation to enforce criminal laws.

"ACT Policing has consulted with both territory and Commonwealth government partners and holds the view that the bill would not negate existing offences within the Criminal Code," Assistant Commissioner Johnson said.

"The removal of ACT offences would remove access to the existing diversion framework … and result in Commonwealth criminal offences becoming the preeminent offence by default."

Assistant Commissioner Johnson said there were 441 cannabis offences over the past five years where the offender was issued a simple fine, keeping them away from the criminal justice system.

ACT Policing said this photo showed how, using wires to support them, just two cannabis plants could be used to grow commercial quantities of the drug. ( Supplied )

But the peak body for the drug sector in Canberra, the Alcohol Tobacco and Other Drug Association (ATODA), said only a quarter of cannabis consumers arrested last year were given a fine, and police overwhelmingly used methods to force people before the courts.

"Cannabis consumers (those who use cannabis but do not sell it) are still arrested in the ACT in the hundreds," ATODA chief executive Carrie Fowlie wrote to the inquiry.

Ms Fowlie acknowledged potential conflicts with Commonwealth law, but said those issues should be tested in the courts.

Allowing growth of two plants per person 'makes ACT attractive to criminals'

Police warned the conflict created tension for officers in how they approached cannabis use, and left them exposed to accusations of impropriety or failure to act.

Mr Johnson also warned legalising cannabis would incentivise organised crime.

In the ACT, people can be either fined or sentenced to two years' prison for possessing up to 50g of cannabis. ( Flickr: Heath Alseike )

"To grow cannabis in any other jurisdiction the crop-sitters carry a significant risk of detection for the entire growth cycle," he said.

"Legitimate growth of cannabis in the ACT would potentially remove this risk, making the ACT more attractive to organised crime groups."

Mr Johnson said cannabis was a significant money maker for bikies, who used it to re-invest in other drugs like heroin and methamphetamine.

His submission warned allowing even two plants per individual, as proposed by the Government, opened the potential for each residence to become a commercial grow house.

He said if conflicts with the Commonwealth could be resolved, ACT Policing supported a cannabis register similar to gun owners.

"This will allow the Government to include licence obligations on growers, including requiring growers to agree to certain conditions," Assistant Commissioner Johnson said.

ACT Policing declined a request for comment.