tweake:
Handle9:
It's impractical to test and therefore almost unenforceable. It smells of one of those laws that sound good on paper but aren't practical to implement.
If it was a massive problem it'd likely get some attention.
not hard to change or enforce.
change it so you have to obey the car manufactures limits and have the correct tow bar for those limits. for enforcement, simply weigh the trailer. thats far easier to do than the "stopping within a distance of seven metres from a speed of 30km/h.". as almost no car/ute has above 700kg unbraked tow limits, and a double axle trailer is ~500kg unloaded, pretty much every trailer bar tiny trailers would require brakes. that makes visual inspection really simple.
it also makes for easy to comply as everyone can look up whats required.
The current law is impossible to enforce. If they changed it they aren't going to change it to make every trailer currently on the road illegal. That would be impractical and largely be ignored.