Trespass is a good example. The law is split into civil and criminal law and depending on jurisdiction and sometimes the status of the land owner (i.e. military, etc), trespass can fall into either camp.
If you break criminal law, you are committing a crime and can be prosecuted and punished for that, on the other hand civil law is characterized as a dispute between two parties and the only crime you can then commit is to flout a court ruling on the matter, which may then progress into criminal law if it is serious enough, or may be referred back for yet more civil proceedings. However even if you do flout a court ruling, and the process becomes criminal, what you originally did remains civil, it is your subsequent conduct towards the court that can be judged as criminal.
If you break criminal law, you are committing a crime and can be prosecuted and punished for that, on the other hand civil law is characterized as a dispute between two parties and the only crime you can then commit is to flout a court ruling on the matter, which may then progress into criminal law if it is serious enough, or may be referred back for yet more civil proceedings. However even if you do flout a court ruling, and the process becomes criminal, what you originally did remains civil, it is your subsequent conduct towards the court that can be judged as criminal.
Here's a good source regarding migration law in the US http://blog.chron.com/immigration/2008/04/being-undocumented...