That sure is strange, given the fact that one has the right to appeal to the courts for relief.
For instance. I am having problems with a neighbour who lets their dog bark through the nite hours contrary to the by-law. The by-law enforcement will not lay charges unless I keep a log of the hours the dog is barking. Because they will not be able to get a conviction. I have had to resort to calling the offending party during the early morning hours and waking them to tell them to keep the dog quiet.
As to an old car, your son should have registered an appeal. I don’t know how you can get plates for a vehicle unless certified to be road worthy by a Certified Licence Mechanic.
This is nothing but a tax renvenue for Barrie. I also doubt they have adequate resources to enforce it. Many by-laws are broken daily by residents of municipalities and nothing is enforced until someone complains. Even then if fine imposed they have to catch you in the act and then you can appeal, that is due process, you can’t circumvent due process.