But that could be a problem even if there are no shelves. That issue is more about what people store in their garages (or in their cages in your case). I can see that a by-law might be beneficial in that case, especially with e-bikes now being so popular.
We also had a tenant who liked to use power tools in the garage, and some were of the kind that produced sparks. There was no by-law in place, and his landlord was disinclined to tell him to stop. Eventually the tenant and his power tools moved out – no action was ever taken. But we’ve digressed from the original question which was specifically about shelving.