The country's Supreme Court (Høyesterett) said in a statement it had ruled "valid" a demand by the Ministry of Agriculture and Food for reindeer herder Jovsset Ánte Sara, 25, to reduce his 150-strong herd to 75.
The herder, who is part of Norway's indigenous Sami community, argued that such a reduction would ruin him and that the ruling would breach human rights norms.
But the court upheld the state's claim that the slaughter was necessary to ensure sustainable management of the land.
The case, which has been through Norway's entire court system, represents the first time a reindeer cull has been judged upon in the Supreme Court.
Sara has vowed to appeal to the European Court of Human Rights.
“Jovsset Ánte was naturally disappointed. We will take the case to the European Court of Human Rights and he will not have to reduce his reindeer herd,” Sara's lawyer Trond Biti Pedersen told NRK.
The reindeer herder said he completely disagreed with the verdict.
“I really thought we had come further than this. The Supreme Court does not seem to be showing that Samis can decide their own fates,” he told NRK.
Lawyer Stein-Erik Jahr Dahl, who represented the state in the case, rejected that claim.
“The state does not think that reindeer herders don't know better, and refers to the high level of autonomy given to the industry in the current reindeer herding laws,” he said according to NRK's report.