Some states (probably provinces too) the DOT does have leverage
In California the DOT and Department of Motor Vehicles have leverage over car dealers and repair shops, and I'm betting it's the same in varying degrees across the continent - because they license the dealerships to buy and sell cars and also issue individual professional licenses to the people who work there.
A lot of the Title and Registration paperwork you file is "Under penalty of Perjury" without a whole lot of double-checking unless there is a problem, and they want to have a way to punish.
And they license the auto repair shops to operate and the people working there for special things like smog machine operations.
In both cases (sales and repairs) it's way too easy to be crooked if the rubes don't know what to watch for. So they do the watching. To the point of test buys and sales, see if the car dealer will buy the car with obvious problems, cover them up, and pass them off to the next guy as a Perfect Car, "and here's the Carfax that shows no issues..." Yeah, because he swapped the VIN with another wreck.
Mechanics, the CA DMV Bureau of Automotive Repair has a whole fleet of Bait Cars that are in absolutely perfect driving condition except for one induced problem (like a set of bad sparkplugs) then they take one in to a suspect shop and see what they are told and sold.
If the shop finds the bad sparkplugs, sell you a new set, don't try to sell you cap and rotor and plug wires because "they look bad..." when they are fine, hand you your old parts back (and the secret marks show they are in fact the right set of old plugs...), and charge a proper price for the labor and materials, they Pass.
It's illegal to oversell unnecessary repairs, and even more so if the shop says they put on a new starter and didn't. They handed you "the old part" that was a worn out core the rebuilders trashed as too far gone...
You make a habit of ripping off consumers, selling wrecked and repaired cars with dummied-up titles, charging for repairs and parts not actually done, cheating on smog inspections, certifying commercial truck & school bus condition and repairs, etc., you end up CLOSED because you don't have operating licenses anymore.