People sharing cannabis with a friend at a party would be still be charged with drug supply, despite new cannabis possession laws legislated on Wednesday.
The ACT's chief police officer Ray Johnson said sharing the drug between people, even when no money is involved, would still constitute as an offence.
"If there's evidence that someone is providing cannabis to someone else, that's supply and that's an offence," he told ABC radio on Wednesday.
Under the new laws, put forward by Labor backbencher Michael Pettersson, adults are allowed to possess 50 grams of cannabis and grow two plants in their home.
The bill passed the ACT Assembly on Wednesday, after debate on several amendments.
Chief Police Officer Johnson said ACT police officers would support the government on the new laws.
"We'll work to make [the laws] as effective as it can be," he said.
"Police officers will have their views, and they'll execute the law of the day as best as they can."
The ACT's top cop said the supply of cannabis seeds would still be illegal, whether they were sold or given away.
While possession of up to 50 grams of cannabis would be legalised, Chief Police Officer Johnson said drug-driving offences would remain the same.
Despite the laws, the ACT Law Society said earlier this week police officers would still be able to charge someone with cannabis possession under federal law.
Chief Police Officer Johnson said a decision on whether someone would be charged under ACT law or Commonwealth law would depend on individual circumstances, and said it would be a challenge for officers.
"If [cannabis possession] continues to be an offence of Commonwealth law, whether or not a police officer chooses to charge an individual and whether cannabis is seized, we've got to work through the fineries," he said.
"Every day, police officers doing their duty do make decisions taking into account the circumstances of the occasion."
The chief police officer said ACT police would still continue to target drug traffickers and drug sellers.
The new laws will likely not come into effect until January and will need to be signed off by the Health Minister.