Okay, here we go:
KIRK: So, they've broken the treaty.
SCOTT: Not necessarily, Captain. They have as much right to scientific missions here as we have.
KIRK: Research is not the Klingon way.
SCOTT: True, but since this is a hands-off planet, how are you going to prove they're doing otherwise?
I don't fucking care wether the klingons call it "the prime directive" or something else, wether they chose to implement it because of moral obligation (probably not) or because they had a treaty with other species, or if they even
like it. The fact remains: The klingons have their own version of a non-interference clause regarding pre-warp civilisations. Period.
How they got it is completely irrelevant to the matter.
Also: Enterprise. I know some people here don't like it. It's still canon. And there It is stated very clearly that Vulcans have a non-interference clause with pre-warp civilisations. As was in the movie "First Contact". Remember that one? You might have seen it.
Romulans have them as well. As was proven by the TNG two-parter "Redemption". They probably don't call it the "prime directive" either. But they have it. Otherwise they wouldn't feel the need to
disguise the act they are violating it during the klingon civil war.
So now you have
all major powers in the Alpha quadrant - the Federation, Vulcans, Klingons and Romulans - adhere to at least some variation of the PD. Also it's established most of those species had Warp-travel way before the humans had it, but they didn't interfere here
either, because we were, again,
pre-warp at that time
.
So yeah, it's not spelled out with crayons. But it's pretty obvious that it's part of a larger understanding between warp-capable civilisations.
There are some days that I wonder if you have actually watched Star Trek...
Ah, back trying to settle arguments with personal insults again?
You almost managed two posts talking to me without them. Almost.