Originally Posted by
Temedar
OP, I believe that TK wrongly denied you boarding, especially since you had proof of same-day travel to France, confirming that it was really your main destination country. The agent's idea that with a French visa "you wouldn't be allowed entry in Oslo or anywhere else outside France" is simply false.
I concur. The situation is not identical but is fundamentally akin to travelling e.g. CGK-AMS-CDG with perhaps an overnight layover in AMS. The OP would be gladly allowed into Schengen in AMS and also allowed to leave the airport as long as they had a valid Schengen visa. Because of the unusual/broken-up itinerary the OP might have to answer a few extra questions at the border, proving financial means for the trip and demonstrating one is a bona fide visitor who will return back to the country of origin, but the formal requirements for entry were certainly satisfied. And whether the formal requirements are satisfied is the only thing an airline should and can check.