Alien Non-Interference Clause

"As the right of each sentient species to live in accordance with its normal cultural evolution is considered sacred, no Star Fleet personnel may interfere with the healthy development of alien life and culture. Such interference includes the introduction of superior knowledge, strength, or technology to a world whose society is incapable of handling such advantages wisely."

- General Order no. 1 (the Prime Directive), Star Trek

Even without ever having met a real culture from outer space, mankind has experienced firsthand the sort of disaster that can come from First Contact between a technologically-advanced society and a technologically-primitive and/or culturally-different one. Case in point: much of the European age of exploration and colonization included a great deal of war, exploitation, cultural assimilation (both forced and not) and even genocide across Asia, Africa, Australia and the Americas, including cultures that, according to modern research, may have been more advanced than we once believed.

It's mainly for this reason that Science Fiction writers came up with the concept of the Alien Non-Interference Clause: in the future, it is believed, people will have learned from the mistakes of the past and take steps from preventing the same mistakes from recurring as humans explore space.

Of course, like the original Prime Directive, such rules are ultimately an Obstructive Code of Conduct that brings conflict to a story. Crash landing on an inhabited world when this rule is in force brings obvious difficulties. Trying to study an alien culture without being discovered is a popular scenario. And where do you draw the line? Is there a point where a species is officially "mature" enough to let them in on the secrets of the universe? Does non-interference mean you're morally obliged to let a species suffer or die because it is their "natural development"? And what will happen when the "protectees" do develop advanced technology and discover that alien races have been watching them Dying Like Animals for generations... and consider themselves pretty darn righteous for their policy of non-assistance? There's also the little matter of how one defines a culture's "normal evolution" or "healthful development"; in addition to the aforementioned "letting them all die" aspect, if a society seems happy but social development has "stagnated", does that justify stepping in to nudge them in the right direction, or should you assume that they might possibly be able to do so in their own time?

A common twist on the trope is to have such a law in effect, and then come across an alien race that is eager to gain tech and knowledge from the humans. What happens then? Can you get away with telling the aliens You Are Not Ready? Where does the rule stop being about "preserving alien cultures" and start being about "keeping the humans (or The Federation) as the dominant power"? One ironic inversion is to have a second, more advanced set of aliens show up and refuse to help because they have this exact same clause, essentially turning the tables and putting the protagonist on the receiving end of this "benign neglect".

Compare Balance Between Good and Evil for a more cosmic variation. See also Low Culture, High Tech; Villains Act, Heroes React (since laws of this kind often forbid higher powers from taking the initiative but do not prevent them from responding to a threat by the lower powers). Protagonists who tend to say Screw the Rules, I'm Doing What's Right usually treat this as a Frequently-Broken Unbreakable Vow.

Comic Books

 * From Marvel Comics: The Watchers have an "observe, don't interfere" law in place (thus their species' name). Eventually revealed to be the result of accidentally destroying another species by giving its members advanced scientific knowledge way too soon.
 * In the Buck Godot Zap Gun for Hire comics, humans are forbidden from interfering with any race not advanced enough for space travel by Lord Thezmothete, because Mega Corps used to enslave such species.
 * Also the Teleporter considered humans to be animals because they couldn't teleport, though he did indeed interfere.
 * In He-Man and the Masters of the Universe, Zodac and other Cosmic Enforcers are tasked with observing all that transpires in the Universe but not interfering except to maintain the balance between good and evil. Because of this on the rare examples when they do interfere they are just as likely to help the bad guys as the heroes.

Films -- Live-Action

 * Hard to be a god is a whole movie dedicated to the dilemma of a human observer on a "primitive" alien planet with one interesting twist: the main reason for his superiors to send him there was to "observe the observer" - see if he would be able to avoid getting involved. (In fact, since 2008, there are two movies.)

Literature
"President: The Federation Council has agreed to waive the non-interference directive."
 * Star Maker, a 1937 novel by Olaf Stapledon (who inspired many of the "golden age" sci-fi writers) has the Symbiont race, Sufficiently Advanced Aliens who keep their existence hidden from "pre-utopian", pre-spacefaring races, revealing themselves only after a race achieves both of those so the fledgling races don't lose their "independence of mind" (pretty similar to the Vulcans that came after).
 * Orson Scott Card's later (chronologically) books in the Ender's Game series, Speaker of the Dead and Xenocide mostly, have had this rule put in place by the Starways Congress years after the obliteration of the Buggers in the first book, and grown-up Ender's writing The Hive Queen about what they were really like. But after Ender gets involved in affairs between the humans and the pequeninos ("piggies") on his new home of Lusitania, it's discovered that the piggies want spaceships, and to become space explorers themselves, in spite of not having passed a lot of technological milestones such as electricity. This causes considerable commotion among the xenologists, and causes them to realize the dark side ("Human superiority first!") of the trope.
 * The pequeninos' attempts at jumping a few branches up the Technology Tree is later described as a sentient species (the piggies) exercising their rights as a sentient species to engage in trade and commerce with visiting extra-terrestrials (humans) for the betterment of piggy-kind.
 * Animorphs has "The Law of Seerow's Kindness", a law passed by the Andalites forbidding them to share technology with less developed species. It was named after Prince Seerow, who passed technology onto the Puppeteer Parasite Yeerks, unintentionally allowing them to become the Big Bad species of the series.
 * The Ellimist and Crayak also have rules about when they can and can't interact with other species, but for a different reason: the Ellimist wants to spread life and freedom, Crayak wants to spread genocide, and any open conflict between them would literally destroy both of them and everything else in the universe. Essentially, they're in a Cold War-style standoff, which is why they each either have to agree to let the other work openly or else act subtly enough to keep the other from knowing.
 * By The Lord of the Rings, the Valar could be said to have taken up a style of this similar to the Ellimist and Crayak: They tried to fight Morgoth directly, and the results were not pretty for Arda.
 * Elizabeth Moon's Remnant Population has "The People", Starfish Aliens who until events in the book, unwittingly share their planet with human colonists. After some humans try to land new colony ships on their nests (and get killed for it), they seek out and find Ofelia, the willing last human of a failed colony hundreds of miles away, who kept the colony's tech running for her own use. Unaware of the non-interference rule (which exists even though humans have never met another intelligent species, as they made many assumptions about what aliens will be like), Ofelia has to show and explain things like electricity to The People, initially so their curiosity doesn't kill them with a high voltage current. But it turns out The People are extremely intelligent and hungry for knowledge, to the surprise of all and the chagrin of the human officials and scientists who get sent to "undo the damage" (some with good but misinformed intentions and some crossing the line into "keeping the humans in charge").
 * Much of the Strugatsky Brothers' Noon Universe novels revolve around various aspects of an Alien Non-Interference Clause and its plausibility:
 * Hard to Be A God investigates how would a human observer fare on a planet stuck in The Dung Ages, while allowed limited intervention at best (for example, he may save a promising scientist deemed heretical by the Inquisition but has no authority to stop the planet from sliding into even further barbarism after a corrupt church gains power).
 * Prisoners of Power revolves around a civilian protagonist unadvertedly crashing on a Dieselpunk world rife with pointless nuclear warfare. He single-handedly forms a plan to overthrow the government and their means of Mind Control... and coincidentally ruins the plan of undercover Earth operatives to solve the planet's issues in a far safer and more gradual way which, however, is implied to take decades if not centuries.
 * Amy Thomson's The Color of Distance and Through Alien Eyes have humanity making first contact with a technologically primitive society of froglike aliens called the Tendu. They have little technology, but they do have impressive medical abilities; they can physically modify creatures, including themselves and humans, and heal just about anything. Humanity has to make reparations for burning down an important chunk of rainforest before they knew the Tendu were there, but they can't violate the protocols in doing so, to the Tendu's frustration; they know what humans have and are fascinated by it. When one of the Tendu decides to come to Earth, he responds to some of the doubts by saying that he, too, will abide by the protocols, and not teach humanity anything that it's not ready for.
 * Also in Darkover by Marion Zimmer Bradley: The humans have a directive never to interfere in the business of aliens, not even if the conflict seems as meaningless as the question how to open an egg. One really wonders who makes such stupid decisions.
 * In CS Lewis's That Hideous Strength, the planetary spirits are forbidden to intervene in Earth's affairs. Unfortunately for the bad guys, they are not forbidden to respond if Earth intervenes in theirs.
 * In Ursula Le Guin's Hainish Cycle, first contact teams are often sent to rather primitive planets, and many such civilizations are incorporated in the interstellar civilization - since it believes that even non technological races have a lot to contribute (arts or philosophy). However, there is an embargo on teaching technology without authorization by the government. The Planet of Exile demonstrates the point when a human is wounded by an enemy dart, and must be careful, since while the natives use no poisons, the Earth Lost Colony does, and the used darts are sometimes fired back.
 * In the Star Trek novel Uhura's Song orders given directly to Kirk by the Federation President and the Commander of Starfleet. To emphasize (to both the readers and the characters) the severity of the situation (a plague that is threatening to cause the collapse of the Federation and kill a large portion of the population of multiple species), the President gives the following statement:


 * That almost-casual statement is the President telling Kirk that the PRIME DIRECTIVE IS GONE.
 * Enchantress From the Stars talks quite a bit about the implications of this trope. Short version: it's worth it in the very, very long run, but damn does it suck in the short run.
 * In Mikhail Akhmanov's Trevellyan's Mission series, humanity and many other starfaring races specifically invert this trope, believing themselves to be dutybound to help guide younger races, although they go to great lengths to avoid revealing themselves. The series goes into great detail as to the criteria for choosing which humanoid species to "progress", as attempts to help an alien species at the wrong stage of development ultimately made things worse for them. Some are hinted to have resulted in extinctions. As such, only pre-Renaissance races are interfered with. On one occasion, the human scientists and their Kni'lina counterparts are debating which of two Stone Age species which evolved on one world to eliminate. The first novel specifically deals with the protagonist attempting to figure out why a world is stuck in Medieval Stasis and why humanity's attempts at making changes utterly fail. It turns out the cause is a previously-unknown advanced alien race who follows a strict policy of non-interference except to stop a major threat against the very survival of the younger races. These "Paraprims" are Technical Pacifists who have descended from primates but are not humanoids (they're more like chimps and still have fur).
 * Usually averted in David Brin's Uplift series. "Pre-sentient" species are nearly always uplifted by the time they reach a stone age level of technology at the latest. However the Institute of Migration often designates planets or even entire regions of space to "lie fallow" for several million years so their ecosystems can recover before allowing re-colonization. Earth was in the middle of a cluster of fallow systems that had been devastated in a war and was overlooked (except perhaps by our mysterious patrons)
 * Thoroughly averted and inverted in Iain M Bank's "The Culture" novels. The Culture, especially its exploratory organisation Contact, see it as their moral duty to make other civilisations (usually those less advanced) more like the Culture (and by implication, statistically better and happier). It usually takes the form of making sure the right rulers stay alive long enough to make their world a better place; whether through alien medicine or impossibly proficient bodyguards and armies.
 * There are factions within the Culture who feel that this practice is wrong, resulting in diaspora like the Peace Faction (who believe in pacifistic non interaction) and the Elench (who believe that they should be the ones changed by alien planets, not the other way round). And this doesn't even count the actions of Contact's darker cousin, Special Circumstances.
 * Elizabeth Bear's novel Undertow has an inversion: If a planet is inhabited, humans can only colonize it if the natives are pre-space. As you might expect, this sometimes results in a situation similar to what happened in most European colonies.
 * But that's not even the best part. The book's major twist is that
 * Patricia Mc Killip wrote a duology (Moon Flash and The Moon And The Face) that discusses this with two dissilmiar cultures on one planet.
 * Gregory Mc Donald wrote Fletch Too about visiting Africa and the discussion arose that concerned the rightness of Africa being put under a glass shield to protect them from technology/interference/etc.

Live-Action TV

 * Star Trek is the Trope Codifier: whether or not they did it first, they're the one most people have likely heard about. The series has been somewhat inconsistent over where the borders of the rule lie. There is usually a hole somewhere "big enough to fly the Enterprise through". The Original Series, at the very least, typically bypassed the Prime Directive by placing the ship and/or the crew in dire peril, with the only solution being one that would devastate/completely change the local society (see "The Apple" or "A Taste Of Armageddon").
 * One Next Generation episode, "First Contact" (no relation to the movie) deals with the justified aspects of the Prime Directive. The Enterprise crew are on a secret First Contact mission to the Malcorians, a species on the verge of discovering Warp Drive. Over wine with the planetary Chancellor, Picard discusses with him the justifications of the Prime Directive and their obligation to leave the Malcorians alone if that is their wish. The Malcorians, who mirror 20th century humans in many ways, are undergoing cultural turmoil because of their rapid march of technology. Meanwhile, Riker was doing covert surveillance when he was injured and hospitalized: it becomes difficult to hide the fact that he's not one of them and he almost dies because the distrustful minister of security tries to use him to convince the Chancellor not to trust the humans. Because of this, Chancelor Durken ultimately decides that his people are not ready to learn they're not alone, though he promises to spend money and effort on education so they'll be prepared when the time comes.
 * In some instances, though, there have been Sufficiently Advanced Aliens who use a similar rule on the Federation protagonists, just to point out how douchey it looks when you're on the short end of it. Big example being "Prime Factors" in Voyager, where aliens that were entirely aware of and even sympathetic to Voyager's situation and capable of transporting most of the way across the galaxy decided that they had to be Lawful Stupid about sending the ship well on its way home. Of course, part of it was that they were just unwilling to lose a potential source of entertainment that Voyager's extensive database could provide. In the end groups of low ranking crew and citizens from both sides just trade for it, and the tech turns out to be incompatible.
 * And then there are the time when they do finally feel justified in breaking the rule such as in the TOS episode where it is discovered that the Klingons have been arming one of the tribes of a primitive planet. Kirk feels its their obligation to offer the competing tribe a similar level of weaponry to defend themselves. In this case, its more of an extension of the existing Cold War metaphor the Klingon-Federation conflict already represented.
 * By the time of The Next Generation, the Prime Directive has been interpreted to prohibit interference in the internal affairs of other cultures even if the culture is an advanced star-faring civilization. This came up during the brief Klingon civil war where the Federation was unable to get involved until they could prove that the Romulans were secretly instigating the conflict to weaken their enemies and/or install more friendly leadership. (Some have more cynically suggested that this is not so much a principle as a convenient excuse.)
 * And ultimately, we learn that the Federation's prime directive is derived from the Vulcans, who would not have made First Contact had they not observed humanity's first warp drive flight.
 * Disturbingly invoked (and possibly incorrectly at that) in an episode of Star Trek Voyager. Janeway and Paris are stranded on a prewarp (but still advanced) planet that is using a source of energy that will literally wipe out all life on the planet the next day. Despite Paris' wish to warn them, Janeway orders him not to, citing the Prime Directive... despite the fact that this interference would literally save everyone and doesn't seem to contradict the actual Prime Directive.
 * Also seen in TNG "Pen Pals". Apparently, extinction is part of a culture's "natural development."
 * In the TNG episode "Symbiosis", the Ornarans are suffering from a fatal disease and are dependent on medicine provided by the Brekkians, but this has lead to the Ornaran society falling apart, while the Brekkians have become so wealthy from the profits that they have centered their entire society on exploiting the Ornarans. It doesn't take long for Dr. Crusher to realize the disease was cured ages ago, and that they were suffering from the withdrawal symptoms; she wants to put an end to this, but Capt. Picard points to the Prime Directive, saying they cannot interfere.
 * Picard then points out they can't interfere to maintain the status quo either. The Ornaran ships were no longer able to make supply runs for the medicine, and they wanted the Enterprise's help in repairing their fleet; by refusing, the Ornarans would have to face the withdrawal and hopefully get over it on their own.
 * Babylon 5 may or may not have had a formal rule but advanced races could and did deny technology to other races believed to be "not ready".
 * In the episode, "Deathwalker", a renegade Dilgar scientist named Jha'dur is captured but bargains her freedom with a breakthrough medication that grants immortality. Before her medication can be mass-produced, she is killed by the Vorlons. Ambassador Kosh tells an assembled audience, "You are not ready for immortality."
 * To be fair the immortality drug required Soylent Green to make, and she intended it as revenge for her species' defeat, gloating that it would prove that they were Not So Different.
 * Epsilon III was declared off limits to all (episode "A Voice In The Wilderness") because the technology of the giant computer contained there would give any one race that got it an unfair advantage.
 * After the Vorlons had left the galaxy, a number of people attempted to travel to Vorlon to lay claim to the advanced technology there; all of them got shot down. Lyta explains that humanity was not presently meant to have Vorlon technology and won't be for about a million years.
 * On the other hand, in the Crusade spin-off series, Captain Matthew Gideon would launch a full spread of modified probes (uploaded with considerable information about Earth and the Interstellar alliance) at a pre-hyperspace planet at the end of Visitors From Down the Street, which abounds in X-Files references. The Excalibur picked up two agents from an alien world who are looking for proof of a government cover-up. They show pictures of Mount Rushmore and old Earth blimps. They also dress in Earth fashions from 200 years go (ie: from the time period at the time of the show's shoot). One of them can speak English because of information stolen from the conspirators. The Reveal: Years before, the government had found itself in a time of social unrest similar to The Sixties. Upon discovering Earth broadcasts, they used them as part of a truly Magnificent conspiracy; manufacture appropriate "evidence", then dispatch The Men in Black to suppress it. The resultant subculture of Conspiracy Theorists absorbed the government's critics and kept them wasting their time chasing "aliens" rather than engaging in civil disobedience. Every crime the government committed afterward was thus blamed on "Outsiders" who secretly manipulated their civilization, permitting them to do as they pleased. Gideon's reasoning for launching the probes to expose the real conspiracy: the government already knew about alien life, and was using humans as scapegoats for unpopular domestic decisions. If that went on unimpeded, they would be a hostile power once they did discover starflight. Gideon's interference was motivated as a rebuttal to the accusations being made against Earth. He was questioned about whether this violated any non-interference principles and replied "Screw 'em."
 * One minor race that embraced the idea was featured in a single episode, and everyone they met reacted with abject horror at their callousness. Other than using the word "inferior" instead of "less advanced" it was basically the original Prime Directive.
 * The Interstellar Alliance has rules about not monkeying about with the cultural and internal affairs of its members, but it also has a Declaration of Principles that all of those members have to sign, so we can be fairly certain none of them have anything really obnoxious in their culture (like killing people for stepping in the wrong field).
 * An important point is that none of the races now around developed hyperspace travel. They all copied it at first, and it dates back to the First Ones. Furthermore, rather than being out of concern for a species development, technology is traded purely on selfish reasons. When Humanity was contacted we sent a few sublight probes to the nearest stars not to arrive until years later. We bought most of our better technology from the Centauri and then developed it. However one thing is clear, joining the Interstellar Alliance gives the nice carrot of artificial gravity to less developed races.
 * The races of the Stargate universe vary in their approach to this. The Tau'ri (Earth humans) reject it and hold it as their duty to help humans and less advanced, non-hostile races on other worlds. They draw the line at giving up advanced military technology (most of the time), especially when it's obvious that doing so would be detrimental. The Tollan follow it strictly after their neighboring planet self-destructed because of technology they were given. The Asgard generally don't share their tech, but make numerous exceptions for the Tau'ri because they're friends. The Ori and the Goa'uld flaunt their tech and meddle all the time, posing as gods to less advanced civilizations.
 * In addition, in one episode Stargate Command discovered an asteroid on a collision course with Earth. They asked the Asgard for help, but the Asgard refused on the grounds that their treaty with the Goa'uld prohibited averting natural disasters. When SG-1 proved that the asteroid had been sent by the Goa'uld, the Asgard immediately provided help.
 * There's also the Ancients, who turn out to have Ascended long ago. Where Star Trek's Prime Directive draws the line at the invention of Faster-Than-Light Travel, these guys won't interfere with those who are still corporeal. Unfortunately, this also extends to (1) what's done with all the supertech they left behind when they Ascended, and (2) allowing evil by fellow ascended individuals, such as Anubis and the Ori. If as an Ancient, you try to stop the bad guys from abusing Ancient tech, or even try to prevent a half-ascended Evil Overlord (whose idea was it to make frakkin' Anubis a candidate for ascension, anyway? No, really, who?) from razing a whole planet, you will find yourself kickbanned right back to corporeality. There's a reason the Neglectful Precursors page has an entire section devoted to these guys alone. Daniel only allowed himself to be ascended to the Ancients' level because he thought he could do more good among them, and is human again now because, well... he was wrong.
 * Of course, the real reason the Ancients are such Neglectful Precursors are because the power we see on the rare occasions they cut loose means they are capable of solving the plot in ten seconds flat. The Ascended Prime Directive is how the writers got out of painting themselves into the corner with finally revealing who the Ancients are (presumably, when all we knew about them was "once upon a time, someone built awesome tech, and then the Goa'uld ganked it," the writers didn't have in mind a race that was nigh-omnipotent and still present.) They could finish the Goa'uld, deal with the Wraith and the Asurans, and bring the crew of theDestiny back to Earth with a thought—the main problems of the three Stargate series, all problems they created by leaving their stuff lying around -- but where's the fun in that?
 * In Stargate Atlantis a coalition of various Pegasus Galaxy civilisations wish that Humanity had one of these. They capture the Atlantis team to put Humanity on Trial over the sheer amount of death and destruction that has occurred ever since they showed up.
 * In Doctor Who, the Time Lords adopted an official policy of neutrality and non-interference, acting only as observers save in cases of great injustice, after granting advanced technology to the Minyans who then destroyed themselves in a series of nuclear wars. Which is not to say they always adhered to it...
 * Or in the Doctor's case, ever. He at least tends to limit his involvement to "stop the threat of the week, then hop back in the TARDIS", and isn't too keen on the idea of, say, 21st century Britain having particle guns. In Aliens of London, he tells Rose that he can't get involved in First Contact, because it's something humans have to do on their own. Once he realizes the aliens are a threat...
 * Played completely for laughs by the time of the 11th Doctor, who explains his Prime-Directive-ish policy to Amy Pond in The Beast Below - she turns away to digest it, and by the time she's turned back, the Doctor has zipped away to start actively interfering on board Starship UK.
 * A child was crying. What did you expect?

Tabletop Games

 * In Classic Traveller, the Scout service asked for Red Zone classification for planets with developing civilizations to protect them from off world interference.
 * Manhunter. The A.T.P.D.S. places Protected World status on planets with young civilizations to stop interference that could change the course of the civilization's natural advancement. It also has laws that prevent its citizens from interfering with the civilizations on unexplored planets.

Video Games

 * The Pangalactic Federation of Star Ocean has the Undeveloped Planet Preservation Pact, which differs from the Star Trek version in that people don't get in as much trouble if they break out the advanced tech to save their own lives.
 * While none of the civilizations of the Mass Effect verse have such a rule, salarian scientist Mordin Solus holds the view that there should be one, citing the fiasco with the Krogan as an example of why.
 * We learn in Mass Effect 2's Lair of the Shadow Broker DLC that when new pre-spaceflight races are discovered, the Citadel sends "First Contact Teams" to their home planets to begin sharing technology, updating translators and explaining Citadel laws and culture to the newly discovered species, preparing them to join the galactic scene. Then they ran into the Yahg, a species even more brutal than the Krogan, who massacred the first contact team. This led to the Council 'blockading' the planet, preventing anyone getting off it - So while they don't hold a general rule requiring it, they do seem to adopt this policy on a case-by-case basis.
 * This forms part of the backstory before the game. The Turians first discovered humanity tinkering with an uncharted Mass Effect relay, trying to turn it on and were forced to intervene because doing so is a major faux-pas in the Mass Effect universe.
 * Of course, instead of contacting the humans and explaining what was going on (how were pre-contact humanity supposed to know an unknown Galactic Law prevents them from tinkering with the relays?), the Turians chose to attack them instead. This started a 3 month long conflict called the First Contact War by humans and Relay 314 Incident by the Turians, which was only ended when the Council was finally was alerted to the situation. The Council were naturally furious to find out that the Turians had performed a pre-emptive strike on an unknown species without getting authorisation.
 * The Geth enforce this on themselves as they believe all species should self-determinate.

Webcomics

 * In Spacetrawler "Dark Planets" home to sapient life with no significant space presence are not supposed to be contacted. The system is still ripe for exploitation: species can be declared non-sapient for spurious reasons like bad fashion sense, and species who do achieve space travel immediately become fair game for any other species to conquer.
 * Quentyn Quinn, Space Ranger had this Deconstructed here. That arc got a postscriptum much later - when we see the good captain again, his first words are
 * Defeated in Schlock Mercenary here.
 * According to RPG materials, the Fobott'r (Andy's species - burly, four handed humanoids with bright crests) had their planet taken over by corporations basically for beads and mirrors. Of course, then those corporations began to hire the locals as security staff and after a while... let's just say, they have their planet back.

Western Animation

 * Parodied by Futurama with Directive B10.8:1 A.K.A. "Brannigan's Law"; the law itself is pretty straight but Brannigan doesn't actually understand it himself, and ends up breaking it at one point.

Real Life

 * The Other Wiki has a list of peoples who have kept culturally isolated or were until fairly recently. Most of them have an estimated three hundred or fewer people (which is not a sustainable population without massive problems due to inbreeding). In general unconnected people are left alone to protect them from disease, or because they are actively hostile.
 * IF (bigger than you can think) there are other civs, this may be the reason they do not contact us.