The law of Arizona requires all registered motor vehicles to carry some minimum amount of car insurance. If a police officer stops a driver, they are allowed to ask for proof of insurance. If a driver does not have it, they can be given a ticket. The driver can fight the ticket in court.
In this scenario, the requirement "must have insurance" is the substance of the law. The officer's right to request proof, the ability to write a ticket to enforce the law, and the motorist's right to fight the ticket, are procedural aspects of the law.
Create an example of a law that illustrates both its substance and its process of enforcement.