UPDATED 12.10pm Protestors have gathered outside the Wellington District Court this morning where 15 peace protestors are to go on trial.

The 15 are among 27 people arrested in 2015 after blockading the New Zealand Defence Industry Association's Weapons Conference, an event principally sponsored by American arms manufacturer Lockheed Martin.​

Sixteen people were due to be trialed but one person has been made eligible for diversion.

About 11 protesters are gathered outside in the blustery weather, holding signs that say "Refugees welcome, arms dealers not".

Other signs said "arms trade death trade" and "war starts here, let's stop it here, no weapons expo".

Lawyers Michael Bott, Chris Tennet and Daniel Vincent are representing some of the group in court, while others have chosen to represent themselves.

The judge-alone trial has begun before Judge Mill.

Prosecutor Catherine Gisler said there were nine charges of trespass, five of obstruction, and one disorderly behaviour.

Gisler said the issues with trespass were "varied".

There were issues over the interpretation of who the "occupier" was in the trespass charge, whether police had the requisite authority to trespass the protestors, and whether the warnings for trespass were reasonable and consistent with the bill of rights act.

There was also a dispute over whether there was any actual obstruction, whether the police officers involved were acting in execution of their duty, and whether the officers' actions were lawful, Gisler said.

The protesters on trial have pled not guilty to charges of obstruction and trespass.

Laura Drew, who is one of those charged, points out that New Zealanders have often protested on issues of international importance.

"In New Zealand, we have a history of resisting these kinds of injustices around the world, like the Springbok Tour," she said. "When we look at what is happening in other places in the world we have to see how that is connected to what we're doing here."

"[The conference organisers] pretend that this is a legitimate business but it's not a legitimate business to make money from killing people."

During the conference last November, more than one hundred protesters prevented delegates from entering the Viaduct Events Centre in Auckland. There were skirmishes with private security, but no arrests were made.