More then likely though it will be through the court system. I am unsure of what would be the "ideal" case for this though.
Our first step will most likely be a case for re-opening the registry for guns folks who already have unregistered machine guns. Several times a year, I speak with people who have had an older relative pass away, and the deceased left a hot potato or two in their gun collection. Right now, their only option is to surrender the weapon for destruction without any compensation.