Jules.. yup , u are right, we cannot take laws into our own hands.. but then, is there any law to say that it is illegal to put up your rear blind ? If there is, then proton/or any other makes cannot install them in the first place..
But, if u ask me, if the car infront of u has the rear-blind up, just overtake or keep a distance, otherwise it is the same as driving behinf a van.