Police executed a number of search warrants on Monday, including on a car and a home in Gordon.

They allegedly found heroin and methylamphetamine, and Van Hieu Truong, 43 of Bonython, was arrested and charged with drug trafficking.

Police, the court heard, had Truong under surveillance using phone taps since July, and the prosecution say he was believed to be dealing drugs on a daily basis.

But Truong's Legal Aid lawyer told the ACT Magistrates Court on Tuesday that police had failed to properly show the link between his client and the phones they were monitoring.

He said Truong hadn't been shown to own a car in which drugs were found, and said the Gordon home police raided was Truong's girlfriend's.

"If this is the extent of the prosecution's case, then it is at best weak," he said.

Police did not attend court to give evidence at the bail hearing, meaning they could not be asked further about the links between Truong, the surveillance and the raids.

Instead, police relied on a bail opposition form to outline the reasons they wanted Truong kept in custody.

The court heard Truong only had drug possession charges on his criminal history.

Magistrate Bernadette Boss acknowledged there was a risk Truong may reoffend.

But Dr Boss said she must be satisfied there was a "likelihood", rather than simply a risk, that he would commit further crimes.

The magistrate said the evidence was not strong enough to support that.

Bail conditions will prevent Truong from contacting his girlfriend, except through a third party about their children, going to her home, and from holding a mobile phone.

He will also be required to submit to urine testing.

The case will be back before court later this month.