Selling anything coming from this website isn't condone. Because it's outright counterfeiting, and this kind of illegal activity can bring down the shopping website AND NintAndBox along.
When a counterfeiter is spotted on eBay, usually members report him/her. However, I don't know what can be done with independent e-shop.
How do yo know that they sell stuff coming from NintAndBox? At least, you can't see the usual NintAndBox marking at the back of the boxes.