This SHOULD be a no-brainer.
Norway has adopted the similar kind of nationalist/socialist environmentalist claptrap supported by the Greens. The idea that trade and agricultural policy should be focused on local supply and "food sovereignty", which of course is just another word for protectionism and rent seeking by farmers.
Norwegian farmers get a lot of that. Around NZ$400 million a year to Norwegian dairy farmers in price, income and other subsidies. For that they can't even produce enough to meet domestic demand. To top that off there is a 29% tariff on imported butter, so Norway already prices imported butter away from its market.
Yet that's not all. You might fairly assume subsidising dairy farmers might mean there is more production than would otherwise be the case, and that the lack of demand shouldn't mean that tariffs get in the way of imports. You're right. Norway also restricts imports to a quota. Only 575 tonnes of butter can be imported under its quota with a tariff of 60% on that.
You see the 29% tariff is actually the general tariff it applies, which is meaningless because of the quota. If there was no quota, the tariff would be 29%, but in actual fact Norway restricts imports of butter and then taxes it.
If there were New Zealand journalists worth their oxygen they would be off to Norway with the Minister of Foreign Trade suggesting a free trade agreement between NZ and Norway to include dairy products (which Norway wont accept, but the media there might raise questions about its ridiculous agricultural trade policies).
There is no need for any country to have a "butter shortage". After all there isn't a sock shortage or a TV shortage or a light bulb shortage is there?