Michigan law requires that all CPL renewal applicants certify that they have completed at least three hours of review of CPL material and have had at least one hour of firing range time within the six months immediately preceding a renewal application.
While the training requirement does not specify that you must take a class, and you could study on your own, a refresher class can help ensure you are up to date on current laws and have an opportunity to improve your skills.
CPL refresher training includes:
Refresher on the laws
Updates on any changes to the law in the last 5 years
Refresher on shooting and conflict avoidance
Proof that you completed the requirements to renew
Range time, with a course of fire that will help you measure your ability and improvement.