Apparently the sale price of nappies are just too good to pass up. Foreigners, mainly from Poland and Lithuania, are coming in and buying up all the diapers and later reselling them online.
No, it's not illegal to buy diapers buy the car load and later resell them online. Some might say, however, that clearing off the shelves of necessity like diapers is a pretty stinky thing to do to your Norwegian neighbors.
Norway is one of the world's most expensive countries. However, supermarkets in the south trying to lure local customers by undercutting rivals on the price of "nappies" inadvertently made it profitable enough for residents of nearby countries to start trading in them.