The Prime Directive seems to grow over time. Originally it seemed more focused on non-warp civilizations, but later it's also a reason to not interfere with internal events in the Klingon Empire.

The original idea seems to be to allow a culture to develop freely, on its own, until it makes contact or is ready to make contact with the Federation or other spacefaring cultures.

But does the Prime Directive apply only to planets? Since it applies to cultures, shouldn't it apply to the mirror universe as well? In the episodes we see where Trek characters have ended up in the mirror universe, they aren't worried about picking sides or causing havoc in their efforts to return to this universe.

While, in The Apple, Kirk says it applies to "living growing cultures," Riker points out in The Last Outpost that they have to let the Ferengi grow, even though they might turn into a threat to the Federation. Overall, it seems, in spite of Kirk (who rationalized a number of violations), that the basic intent of the Prime Directive is to not judge other cultures and to allow them to develop without Federation interference.

So wouldn't the Prime Directive apply to the mirror universe, or any other alternate universes, as well as just to planets or cultures in this universe?

  • 2
    Do they interact with warp incapable groups in the mirror universe?
    – user1027
    Jan 21, 2015 at 2:36
  • they aren't worried about picking sides or causing havoc in their efforts to return to this universe You need to cite concrete examples so we can judge whether or not the PD is indeed applicable in those cases. Otherwise this question is not very useful.
    – Vector
    Jan 14, 2018 at 4:08
  • @Vector: I provided one in the question.
    – Tango
    Jan 17, 2018 at 3:03
  • I provided one in the question I don't see it.
    – Vector
    Jan 17, 2018 at 20:20
  • Pretty much any visit to the mirror universe, as cited. Shouldn't need to be broken down any more than that.
    – Tango
    Jan 17, 2018 at 21:20

3 Answers 3


I'm going to go out on a limb here: Yes, it is limited to this universe.

There is no direct canonical evidence for this, but a great deal of indirect evidence.

As I bring these examples up, please bear in mind that (various poorly-written episodes notwithstanding) Starfleet personnel are normally expected to give their lives to uphold the Prime Directive. What we see, time and time again, is the exact opposite of this. Decorated officers completely ignore the Prime Directive, usually to save their own lives, and not only are they not punished, the PD isn't even brought up as an issue, then or later.

First, consider "Mirror, Mirror" (TOS) (we're skipping ENT because the Prime Directive was not yet in force at that time). Kirk quite deliberately alters the course of history in the mirror universe. What's more, he does so by persuading mirror!Spock to completely change the fundamental principles of the Terran Empire. I should also note that Kirk describes the mirror universe as "savage," and Spock calls its inhabitants "uncivilized." Since the Prime Directive seems to apply especially strongly to less advanced races ("First Contact", TNG, and many other episodes), this is quite telling.

Jump ahead to "Crossover" (DS9). Kira and O'Brien participate in a small-scale rebellion within the mirror universe. This rebellion is strongly implied to have ultimately succeeded, at least at the local level. Again, they changed the course of history in a drastic fashion.

When Picard suggested intervening in the Klingon Civil War, Fleet Admiral Shanthi initially rebuffed him, until he argued that the Romulan Star Empire was likely involved as well ("Redemption II", TNG). This suggests the Prime Directive specifically forbids becoming involved in somebody else's purely internal rebellion or civil war, even if the "somebody else" is (at the time) a close ally of the Federation.

Later, in "Through the Looking Glass" (DS9), Sisko further aids that same rebellion, impersonating its leader (his late mirror self) and persuading mirror!Jennifer to join the rebellion. In "Shattered Mirror", he assists in the repairs of the mirror!Defiant, and even captains it briefly, all to support the rebellion.

I can't find any clear PD violations in (Memory Alpha's summary of) "Resurrection" (DS9).

While DS9 has a few other examples of characters interacting with the mirror universe, the most blatant violations (in "The Emperor's New Cloak") were not carried out by Starfleet personnel, so I can't really fault them here.

So far as I'm aware, at no point in any of the live action shows or movies does anyone bring up the Prime Directive in relation to any parallel universe. The silence here is deafening. On numerous occasions, parallel universes are altered to suit the needs of our main characters, and at no point is this regarded as violating the PD. In DS9's "Playing God" (props to @Keen for catching this), ethical issues are brought up, but the PD is not. At some point, we have to draw the obvious conclusion: The Prime Directive is never mentioned because it does not apply.

  • 2
    @Oldcat: Mirror!Spock would not have done so, but for Kirk. The mirror universe would be a very different place if Kirk had never been there, or if he had quietly allowed himself to be executed. That's interference in my book.
    – Kevin
    Jan 21, 2015 at 0:01
  • 3
    Kirk uses a different book entirely. See all the shows where he overthrows a computer overlord.
    – Oldcat
    Jan 21, 2015 at 0:03
  • 1
    The fact that Kirk likes to bend the rules is irrelevant. This is like going back in time and convincing Beethoven that he shouldn't go into music. Sure, technically you didn't change things, but the music world will still hate you for it (assuming they remember).
    – Kevin
    Jan 21, 2015 at 0:06
  • 1
    @Oldcat considering I checked multiple definitions and etymology so make sure there was no super secret pun based on sound, that's just plain ableist...
    – user16696
    Jan 21, 2015 at 2:28
  • 2
    There was also that DS9 episode involving a baby universe.
    – user1027
    Jan 21, 2015 at 2:35

I would think, since it is supposed to be quite rare to travel to alternate and mirror universes, that the prime directive is probably legally ambiguous in this arena. So far I haven't been to find any evidence of direct mention that it does apply.

Since it is so rare and theoretically even more rare for someone to actually return from another universe it hasn't been given much attention. Due to the fact that it happened to Kirk and it seems most characters from DS9, you would think that someone at Starfleet headquarters would have addressed it by now. But like androids being sentient beings with rights, it is probably still legally ambiguous at best in this situation.

Most characters seem more focused on just getting back to their own reality, which given the situation is probably best for the prime directive anyways.


Unless a SF vessel is cut off from Starfleet and the Federation at large, I would say 'no'.

But, the Prime Directive would apply either way because its something SF officers usually live by (its their sworn oath)... I don't think it matters whether they are in their own universe or not.

If a ship is cut off from Starfleet/Federation an in another universe, I would imagine that the crew could begin to view the PD in a slightly more flexible manner... but only if the circumstances forced them to and it became a matter of survival (short of becoming thieves and killers).

Remember that Picard and his crew also broke the PD... and they were fairly near Federation space when it was done.

Janeway also 'bent' the PD on several occasions (though it could be constituted as 'breaking' it rather than 'bending).

I think the 'circumstances' of breaking the PD are just as important as anything else... and if the ship/crew return to the Federation, their actions (and circumstances behind breaking the PD) will be reviewed and contrasted to everything else they did.

Look at captain Ransom and USS Equinox. They systematically broke the PD to such a degree where they ended up killing sentient life-forms jut to get home a bit quicker. SF officers were trained to deal with the trauma of losing people and to deal with the 'unexpected'... which I agree can sometimes be a problem because they cherish 'life' above all else, but I thought the Equinox crew actions were ridiculously uncharacteristic of what SF officers would do.

Even if you end up losing a third of your crew, you don't turn to violence and murdering to get home a bit quicker. You get your bearings, try to find a relatively safe space, and then use the freaking advanced technology you have at your disposal to repair your damage and move on... mourn when you can afford to.

Janeway at least was ready to destroy Voyager in order to prevent it from falling into the hands of Kazon for example.

Anyway, Sisko, Kira and Bashir ended up in the Mirror Universe... but mostly as prisoners. They were technically abducted and forced to do things for the MU counterparts. Sisko made a bit of a bigger felony in this regard.

Though to be fair, it is difficult sometimes to see what constitutes as 'interference'... especially if you're dealing with similarly advanced races. Interaction alone can be seen as 'interference' depending on the circumstances.

At any rate, there are matters of degrees to the situation, but I don't think going into another universe matters. The Prime Directive would probably apply. Just because you're in another universe, it doesn't provide the leeway to suddenly do whatever the heck you want.

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