Warnings about ‘slippery slopes’ are often overused by defenders of individual liberty. That’s probably inevitable, since we often end up defending a principle against a seemingly-pragmatic policy that, by itself, is not very objectionable.
For instance, I find it hard to muster any specific argument against energy efficiency labelling of washing machines, but the principle of letting people do what they want with their own stuff means that I’m still pretty suspicious of them. It’s hard to convince someone else who doesn’t already share my belief in that principle without resorting to things like slippery slope arguments .(First they label the washing machines – next it’ll be health warnings on cans of Coca-Cola!)
But, overused as they can be, slippery slopes really do exist. Tobacco regulation is an interesting example, because it's often used as the thin end of the wedge for other kinds of paternalism. After plain packaging of tobacco was passed in Australia (will the new, nominally Liberal government repeal this legislation?), its advocates moved straight on to calls for plain packaging of alcohol. To quote our 2012 paper :
Australian Senator Cory Bernadi recalls: “[O]n the very first day [after the plain packaging legislation was passed] they moved onto drinking. People who were advocating plain packaging were saying “We should have this for alcohol. We should have it in fast food”. Where does it end? The nanny state will never end because there is always another cause to advocate for.”
Some health groups in Australia have also called for plain packaging of ‘junk food’, whatever that is.
So it’s worrying when tobacco is treated as a special case in international trade agreements, as is happening in Trans-Pacific Partnership negotiations between a number of major Pacific Rim countries, including Australia, the US, New Zealand and Japan.
The US and Malaysia have proposed exemptions  for domestic tobacco control measures from the provisions of the Partnership. Not many people will object to that on its own, but here’s where the slippery slope problem comes in. Most free trade agreements are riddled with special exceptions, but using them to reinforce domestic paternalism is particularly ugly.
A free trade agreement that institutionalises tobacco as being ‘non-normal’ is a hop, skip and a jump from one that does the same for all sorts of other things that people probably would have a problem with being told are abnormal, like booze. And the infantilization of adults – much harder to pinpoint than the number of lives supposedly ‘saved’ by tobacco control measures – rolls on.