Mr. Laser Beam wrote:
If Worf was allowed (albeit reprimanded) to kill Duras, then why would he not be allowed to deal with Kurn as he saw fit?
Was it because Worf killed Duras on board a Klingon ship, and this thing with Kurn was on DS9?
Worf was not allowed to kill Duras. Worf killed Duras, and then Picard chose to only discipline him by giving him a stern speech about being a Starfleet officer. Legally, though, the reason it wasn't prosecuted as murder was that it happened in klingon jurisdiciton.
Similarly if Worf had taken shore leave and killed Duras on a Klingon planet it also would not have been prosecutable by the Federation.
Yet Worf killed Gowron on DS9
and he was never arrested for murder.
It's one of those grey areas, Worf acted within Klingon Customs. As I believe someone else mentioned, if Sisko was an example to go by, Starfleet might not have been to sad to see the back of Gowron who was risking the entire war effort will poorly conceived plans.
Besides the room the fight took place in could have been granted embassy status, gien that the leader of the Klingon Empire was there.
Though in the case of Gowron it's rather Ironic that Worf was responsible for both his rise and fall as Chancellor.