That is the key question a court will consider after three pro-life supporters pleaded not guilty to protesting in the exclusion zone around Canberra's abortion clinic.

Last year the ACT parliament introduced a protest-free exclusion zone around the health clinic on Moore Street in Civic.

The laws made it an offence to engage in prohibited behaviour - including protest - in the protected area.

Kerry Mellor, 76, John Popplewell, 76, and Ken Clancy, 78, are the first to be charged and brought to court under the law.

On February 3, they were each fined $750 for protesting in the protection zone.

The men admit they oppose abortions being carried out at the clinic, and they admit they were in the protected zone on that day.

They deny what they were doing was protest.

In videos tendered to the court, one man is seen sitting on a bench holding rosary beads. The other two men are seen, separately, walking along the street.

The building manager told the ACT Magistrates Court as the hearing got underway on Tuesday that she had witnessed for years people gather outside the clinic on a Friday morning.

Branka Milanovic said before there was an exclusion zone, the group brought anti-abortion materials and props like a crucifix, bibles, rosary beads, and a wooden box that held a plastic fetus inside a uterus.

She told the court that when the zone came into law the group moved across the street to outside the PJ O'Reillys pub and no longer brought props.

She said when the exclusion zone was later expanded, members of the group would walk alone around outside the clinic.

A security guard also told the court he saw the men on February 3 praying and walking around with rosary beads.

This was challenged by the defence, who suggested the security guard had not seen either of the two men walking holding rosary beads.

Defence barrister John Purnell SCalso challenged the security guard Greg Brkic on his suggestion that the men were praying.

The barrister asked Mr Brkic if he had heard anyone praying that day.

"No, because they're not praying out loud," he replied.

"Exactly," Mr Purnell said.

Prosecutors will argue that the three men's conduct that day amounted to a "protest, by any means".

Prosecutor James Walker said in his opening address that the law was broad and meant to catch a wide range of conduct.

He said the men's actions were a protest and followed from when and where the prayer vigils occurred, and also the men's opposition to abortions.

Magistrate Glenn Theakston earlier on Tuesday had also granted a Crown application to lead "tendency evidence".

The Crown will argue the men had various tendencies - including that each felt compelled to demonstrate his opposition to abortions - in attempting to prove that what they did on February 3 amounted to protest.

The court has also heard the three men have flagged a constitutional challenge, arguing the law is invalid because it infringes the implied freedom of political communication.

The hearing continues.