As twisted as it is, this is actually old news (but Dutch media picked it up again too). About two years ago, something similar came up with pit-bulls and other fighting dogs that could be deducted from tasks if one bought them 'for business.' Criminals could buy dogs as weapons or deterrents, and deduct their costs.

As I understand it, it has little to do with tax though. We have a law here that lets government seize the profits made by criminal enterprise (translated: “pluck-them law”). The costs of said gun (or dogs) are deducted from the total amount that can be ‘plucked’ from the criminals in question. That’s the saving under discussion. This means that before a criminal can deduct the costs from his gun, he first must've been cought an convicted.

Still, it's an odd rule. I really don't get why there hasn't been made changes in legislation to stop this behavior - I guess that there are more pressing matters to attend to first.

<edit>

I found another example: Farmers of marihuana (who, in contrary to popular belief, are criminals by Dutch law) are able to deduct the costs of the plants/seeds and the rent of the hanger where they grow the stuff.