The trial of an Aboriginal activist charged with stealing a bronze plaque from outside Old Parliament House in Canberra has started in the ACT Supreme Court.

It is alleged Kevin Buzzacott, 57, led a protest outside Old Parliament House in January 2002.

The court heard he used tools to remove a bronze coat of arms from the building and took it back to the nearby Aboriginal tent embassy.

Defence lawyer Len Lindon told the court that Buzzacott's arrest is part of an ongoing campaign to remove the embassy. He also made several references to Indigenous people losing their land to Europeans.

Outside, Buzzacott said the court does not have jurisdiction to hear the case.

"I shouldn't even be here, I should walk away from this court, they haven't got jurisdiction or authorisation to arrest me," he said.

The prosecution told the court that police tried unsuccessfully to have the plaque returned on the day, but they had to get a warrant to search the area two days later.

The trial is expected to last three to four days.