The Greens believe prison terms should be limited to the most violent criminals.
They favour more rehabilitation centres and diversion schemes.
Offenders would have to accept responsibility and show remorse for their crimes and, if a victim wished, make a personal apology.
Full restitution to victims would come before the payment of court fines.
After keeping a clean slate for 10 years, people would have criminal records for minor offences wiped.
The Greens also want a moratorium on the building of prisons and oppose the privatisation of jails.
Private ownership of automatic weapons would be made illegal.
Mr Tanczos, who is a member of the Wild Greens, which vandalised a genetically engineered experimental crop in Canterbury, said justice was a major issue for the Greens and central to their social justice philosophy.