I notice that the proponents of this law claim that the evidence of the harm that can be caused by secondary smoking provides prima facie justification for banning smoking in cars. Prima facie evidence points to great health risks of many, many activities that parents oblige their children to participate in, some with far more serious consequences for their wellbeing. In order to argue for this ban isn't there a burden of proof on its proponents to show that other more dangerous practices are being prioritised ahead of this measure?
If this isn't the most serious threat to the health of minors then what is the motivation behind this move? And what justification are its proponents using to shuffle this kind of measure to the top of the list?
Personally I have a problem with using legislation to engineer personal behaviour change amongst the citizenry. Of course that's not a blanket objection, but it does mean that when the law seeks to interfere in the arena of private behaviour the burden of proof of harm needs to be very stingent.
I really would be interested to see any peer-reviewed medical data linking secondary smoking in cars to negative health outcomes.