Virtually all legal systems do categorize illegal offences in two or three degrees of seriousness. We propose a distinction between two classes of offences: crimes and contraventions.
Contraventions are light offences, i.e. things we do not want people to do but also we do not deem as serious as we feel it necessary to punish them severely. Think about littering or walking your dog unleashed in urban areas.
Crimes are the serious offences which really disrupts society and require a much tougher response. Think about murder, robbery or possession of explosives.
In our proposal we do not consider it necessary that people who have committed a contravention should get a criminal record. Therefore we are in favour of punishing contraventions with administrative sanctions (mostly fines). If the government, this would be in many cases the police, establishes you have been guilty of a contravention, you will get a fine. And if you disagree with this penalty you can bring the case to court.
Those who are suspected of crimes will stand trial in criminal court. If they are convicted they will get a criminal record, which will not happen to those who only commit contraventions. Further the penalties for crimes will be much more serious.
A further distinction between crimes and contraventions is that attempting or preparing a contravention will not be punishable, but attempt and preparation of a crime would be.