A hearing is due to begin in the Supreme Court on Tuesday for 12 of those charged following nationwide police raids in 2007.
Those arrested face a number of charges under the Arms Act. Five are also charged with participating in a criminal group.
Tuesday's hearing is about evidence to be presented at the trial, but most details of the pre-trial hearings have been suppressed.
In March, the Court of Appeal upheld an earlier High Court ruling that the accused should have their cases heard by a judge, rather than a jury, but several of the accused have sought a Supreme Court hearing on that point.
The trial is due to take place in Auckland at the end of this month.
