A comment on health policy implies a possible principle of political justice:

[Health Secretary] Andrew Lansley has no more business nudging smokers to stop and putting tobacconists out of business, than he would trying to force non-smokers like me to take it up and subsidising the industry.

It’s interesting to wonder whether this would work as a principle across the board: in many cases I think it has a definite ring of insight, but I wonder whether the author would endorse its extension to, say, a rule that a government may no more prevent unlicensed drivers from using the roads than it may require everyone to become a (licensed) driver. If a general principle on this model were shown to enjoy a strong rational defence, it could imply quite a strong form of libertarianism.

In practice, I should imagine that the most obvious counterargument would be grounded in asymmetry of consequences: those discouraged from smoking are shunted away from the risks it involves, whereas those ordered to smoke are pushed towards them. Another possible line would involve resources: those ordered to smoke would be ordered to expend funds on the practice, whereas those nudged away would retain the money they would otherwise have spent on smoking, and would be free to spend it on anything the government approved of. The catch with these ostensibly freedom-expanding counterarguments? Ask Isaiah Berlin.