The boy traveled from Sweden to Denmark in April last year with the intention of murdering at least one person with connections to the Comanches motorcycle gang.
But the people were not at the address the boy went to. Shortly afterwards, he was arrested by Danish police with two guns.
The Swede, who was 15 years old at the time, was sentenced to five and a half years in prison for attempted murder at Frederiksberg District Court earlier this year.
Unlike the district court, the Court of Appeal finds that the boy, who is now 17 years old, can also be sentenced based on a section that provides harsher punishment for possession of weapons in public places.
