How common are import bans of what is freely traded on national markets?

In this question I will give an example of a law that effectively bans the import of (and makes attempted import without prior approval a crime) certain goods that can be freely bought and sold on national market. The effect is that the goods are hard to find and cost 10 times more than in countries where such a ban does not exist.

The actual question is: how common is this scenario in free/democratic countries? Is it common, or is the below example just a legal anecdote that ideally needs to be fixed by lobbying/pushing the law makers in the right direction?

In New Zealand, people over 18 can freely buy and sell air pistols. No firearms license is required (unless you are younger than 18).

However, if Bob wants to buy an air pistol from say Amazon, he needs to apply to the Police for a permit to import. The most amazing/amusing thing here is that, unlike real, non-air guns (e.g. a regular rifle, an application to import which can be considered just by any "member of the Police" who "must" grant it if certain criteria is met as per section 18(2,3)), an application to import an air pistol (which is "restricted airgun") has to be considered by the Commissioner (the head of the NZ Police themselves) who only "may" grant it, and only if there is a "special reason" to it (section 18(4,5)).

The law does not elaborate on what "special reasons" are, but the Police still has its idea. In a nut shell, if Bob simply wants to practice target shooting with an air pistol at his rural backyard, or control the population of rats threatening his duck flock, he is out of luck: import is effectively banned for him. But he still can just buy the same thing locally — if he is lucky enough to find it.

Now, there is more to it. Say Bob, who routinely buys stuff from Amazon, sees there an air pistol he wants for only $50, new, whereas locally he can find it only for no less than $500, used. He orders it without hesitation, thinking that if he can freely trade and use it locally, surely there will be no troubles buying it from overseas. He has no idea that there is section 16 which, in its previous version could send him to jail for 1 year (in the current version they’ve added "without reasonable excuse" which now could possibly save Bob from becoming a prisoner). Bob’s Amazon order arrives at the customs which, upon not finding a matching import permit, forfeits it by way of transfer of title to the Crown. Bob loses the money — getting punished for not being clairvoyant enough to expect that such a law could exist. Moreover, he should be thankful that no charges get laid against him.

Apparently, the legislative intent here was to limit the number of air pistols in the country: if they were as accessible as they are in the world, the number of crimes involving them would have gone up. However, managing the risk of unlawful use just by keeping the prices 10 times higher (as opposed to either completely banning trade/possession or applying the same "special reason" threshold as for import) does seem like a very odd, peculiar solution.