Actually, the law in question, “Lov om dyrevelferd” (1) (translates to “law on animal welfare”) makes no mention of kosher or halal. The law concerns itself with the welfare of animals, dealing with a wide array of issues concering animals such as medical testing, the use of barbed wire, violent or sexual abuse of animals and of course, slaughter.
What it does say about slaughter is that when an animal is killed, it must be sedated to the point of unconsciousness and remain so from before the killing starts until the animal is dead. (1, §12)
As a consequence of this law about animal welfare, traditional halal and kosher slaughtering is illegal in Norway, as they both prohibit sedating the animal before slaughter. (2)
However, the Islamic council in Norway have given non-traditional halal slaughter methods which include sedating the animals as well as the other restrictions given in the law on animal welfare their blessing. Thus meat from sedated, legally slaughtered animals are sold in Norway as halal meat. (3)
1) http://www.lovdata.no/all/tl-20090619-097-001.html#12
2) http://en.wikipedia.org/wiki/Dhabihah
3) http://www.nortura.no/nyhetsarkiv-2008/historisk-avtale-om-halal-slakting-article21128-13689.html
