The Oslo appeals court said it was not competent to offer such a pre-emptive guarantee since Snowden had not set foot in Norway and Washington had not submitted a formal request for his extradition.
The former National Security Agency (NSA) contractor, who lives in exile in Russia, faces US charges of espionage and theft of state secrets that could land him up to 30 years in jail.
The charges followed his 2013 release to the media of the extent of the NSA's surveillance programmes.
The appeals court upheld the June ruling of a lower court to which Snowden had taken his challenge against the Norwegian justice ministry's position that no guarantees on extradition could be given before a request had been formally received.
The Norwegian branch of the PEN Club has invited Snowden to Oslo on November 18 to collect the Ossietzky prize, which celebrates "outstanding efforts for freedom of expression."
Reacting to the ruling, Snowden tweeted his dismay.
"The government of Norway is fighting to prevent presentation of a freedom of speech award. Talk about winning a battle instead of the war," he wrote.
Norway's branch of the PEN Club said it would appeal the case at the Supreme Court.
Norway was one of the countries where Snowden had sought asylum when he fled the US in 2013, but Oslo's response was that asylum seekers had to be physically present in the country to apply.
Considered a whistleblower by some and a traitor by others, Snowden won a similar Norwegian award in 2015, but was unable to collect it in person for the same reason.
Snowden has also been nominated for the Nobel Peace Prize, also awarded in Norway, for a third straight year. This year's award will be announced on October 7.