Katherine Woskett, 27, and Patrick Kieren Holmes, 26, staged the dramatic protest on December 1, 2016.

While suspended above the Parliament House grounds in Canberra they unfurled a banner just below the Australian coat of arms that said "Close the bloody camps now. #Justice4refugees."

The two, who are based in Victoria, did not appear in the ACT Magistrates Court on Tuesday where they were to be sentenced for a charge of disorderly and offensive conduct.

Their defence solicitor Tim Sharman said on their behalf that the purpose of their protest was to attract attention to the plight of refugees in the detention camps on Manus Island and in Nauru.

He said Woskett was a qualified arborist and rope-access technician, and Holmes was a high-rise window cleaner, and they had taken precautions for their safety and the safety of others.

He said "history would be the judge" as to the object of their protest that day but he told the court they admitted they broke the law and pleaded guilty to the offence.

Federal prosecutor Edward Chen said the offence, which carried a maximum penalty of a fine of $3600, needed to send a message of deterrence.

He said their actions had diverted the resources of five separate emergency response teams including ACT Policing, ACT Fire & Rescue, AFP Search and Rescue and AFP Special Response.

The court heard that the incident was resolved that same morning after emergency services gave the pair a deadline to descend by 10.30am.

They lowered themselves down four minutes before the deadline and were subsequently charged.

Magistrate Glenn Theakston noted that Woskett and Holmes were not in court on Tuesday and there was no evidence of their remorse or contrition for the offence.

He convicted and fined the pair $1500 each, giving them 12 months to pay.

Last week, protesters who staged a Department of Immigration sit-in on November last year escaped a conviction.