You can totally have aliens in your fantasy narrative. They don’t even have to come from outer space; they can just be from another country.
“Alien,” in the strict sense, just means “not one’s own.” As such, we use the term on a mundane level for anybody who’s an outsider: foreigners in particular, but depending on context, sometimes just a person from far enough away within your own country that they seem a bit, y’know, different.
And difference has, historically, been kind of a scary thing. Xenophobia is far from new; our brains are very strongly wired to distinguish between Our Monkeys and Other Monkeys, and to favor the former. (Yes, I realize we’re apes, not monkeys, but slang prefers the latter term.) There’s something of a biological underpinning for this, since genetically it’s a good investment to help out people who are related to you rather than those who aren’t. But really, our brains probably care more about known vs. unknown: I recently read about a study where a free rat will quickly help free a trapped rat that’s part of their community, even the latter isn’t biologically related, but will ignore a related rat they aren’t acquainted with.
What’s changed over time has generally been the location of that boundary, the line between My Monkey and Not My Monkey. When you live in a small farming community and rarely travel more than twenty miles from home, a hundred miles away might be alien territory. Robert Jordan did a nice job of depicting this provincial mindset in the first Wheel of Time book, with his characters from Emond’s Field stereotyping the residents of Taren Ferry as untrustworthy . . . when the two villages lie barely a day’s travel apart, and both of them tiny specks in a much, much larger world. Living in twenty-first century California, I consider people three thousand miles away in Boston to be my fellow citizens. But then, it isn’t just about distance: I might have more in common with and feel more common cause with those Bostonites than I do with the rural population of Wyoming.
Where the law is concerned, the boundary is usually — but not always — set at the level of the sovereign polity (an awkward phrasing I’m using because there are, after all, different kinds of polity, and one of these days I’ll get around to discussing the technical distinctions between e.g. a country and a nation). I say “not always” because a subdivided polity that’s interested in controlling its populace might also set boundaries between one province and another, or even on the level of one village vs. another, such that there’s a meaningful legal status associated with being in a village not your own. But since in modern times we’re mostly concerned with people from another sovereign state, we’ll speak of it here in those terms.
States like to keep track of aliens within their borders because those people make things complicated. Whose laws apply to them, in what situations? Who gets to levy taxes on them, and for what purposes? Whose interests are they serving? What information are they passing home, and are their intentions in doing so innocuous or nefarious?
The answers to those questions will depend a great deal on who the alien is, of course. An ambassador is assumed to be serving the interests of their homeland and to be reporting home regularly. A merchant’s taxation status may be complicated, and historically there’s been a tendency to assume they’re a spy, because merchants have such a good excuse to travel back and forth and talk to different people. A refugee, on the other hand, probably won’t go back home . . . but xenophobia means we’ve had disproportionate fears that enemy agents are sneaking in under that cover to work against the interests of their host country.
It’s also relevant whether the alien’s stay in another land is short-term or long. Resident Alien may be the title of a SF comic book and TV show, but as a term of law it just means somebody who’s doing more than merely visiting — someone who’s legally residing in another land. These are generally the people we’re referring to when we talk about immigrants: the ones who are here to stay.
Naturally, xenophobia rears its head here as well. Often this revolves around economic concerns, i.e. “they’re coming to take our jobs.” That’s particularly true when the immigrants are either skilled workers in a certain profession (in modern times, that might be tech; in the past, something like weaving) or else willing, by dint of necessity, to perform scut jobs for lower pay than a local might demand. But differences of religion often play a big role here, too — even when the religion in question is theoretically the same one. I might be Catholic and you might be Catholic, and the term “catholic” might literally mean “universal,” but it’s still entirely possible to be the wrong kind of Catholic, and thereby to evoke suspicion and prejudice.
Despite that, many societies have had ways for aliens to shed some or all of their outsider status — at least, in the eyes of the law. Rome had a number of different citizenship rights, and degrees of belonging that might grant some but not all of those rights. The Inca distinguished between three troups: their common subjects, “Inca by privilege,” and “Inca by blood.” It was possible to make a particular group Inca by privilege, but never (I believe) by blood, echoing the jus sanguinis concept I mentioned last week. Britain for several centuries had a process by which an alien could become a “denizen,” with the right to hold but not inherit property, and the right to vote in elections but not hold a parliamentary seat. Nowadays the process of joining another country is referred to as naturalization and tends to be less piecemeal, though some distinctions may remain: to become President of the United States, you must hold birthright citizenship, though there have been proposals to alter that rule.
What’s required to become a naturalized citizen? Not only does that vary, but you can learn a lot about a country by the requirements they enforce. A certain duration of continuous residence is common, but other components may include a relationship (e.g. marriage) with a citizen, military service, language proficiency, passing a cultural exam, an oath of allegiance, payment of a fee, and more. One big shift in the last hundred years has been the streamlining of affairs so that people can be naturalized en masse; naturalization in Britain (as opposed to the easier denization) used to require a private act of Parliament, which would be utterly impractical for the scale of immigration the modern world experiences. We’ve also seen a slow shift toward allowing people to hold citizenship in multiple countries, though that practice is far from universal at the moment.
Naturalization isn’t the end of the road, of course. Prejudice, culture shock, and homesickness can endure for a long, long time. But compared to the laws and mentalities of the past, we have become remarkably accepting of aliens among us.