The phrase describes a process to make sure that people using parking facilities are following the rules that have been set at that specific property.
People sometimes make mistakes when parking or deliberately ignore the rules of the car park.
Typical reasons that someone might get into trouble include:
- Not noticing any signs about ownership or rules
- Mis-keying their vehicle registration into a keypad when paying.
- Overstaying the maximum time limit of the car park
- Forgetting to pay for the parking on entry or exit
- Being chased about a vehicle you don’t own
- Various other reasons
The important thing is that the enforcement companies have permission (i.e. a legal contract) from the landowner (e.g. a supermarket) to manage that private land and to enforce parking rules.
They must clearly display those rules, typically at the entrances to the car park and near payment stations. The rules must be absolutely clear and possible penalties should be detailed on the signs.
This is all absolutely legal. You make a civil contract with the landowner when you park on their land. Any breaches of that agreement are enforced by Civil, not Criminal, law. In other words, you cannot be arrested or sent to prison for breaches of the car park rules.