Let's break this down into a couple of questions, because context is king:
**What's the Fourteenth Amendment, anyway?**
Basically, the rule is that if you're born in the USA, you're a US citizen. The Fourteenth Amendment states it pretty clearly. It begins:
>All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.
If you're born in the USA, you have what's known as [*jus soli*](
https://en.wikipedia.org/wiki/Jus_soli) citizenship: citizenship by place of birth, as opposed to [*jus sanguinis*](
https://en.wikipedia.org/wiki/Jus_sanguinis) citizenship, which comes from blood (that is to say, from your parents' citizenship). (There are *some* exceptions to this, like for example the children of diplomats who aren't 'subject to the jurisdiction thereof', but these are rare. Generally speaking, if you pop a sprog between Canada and Mexico, that kid has US citizenship by birthright.) This has been considered pretty much a settled question in jurisprudence ever since about 1898, in [*United States v. Wong Kim Ark*](
https://en.wikipedia.org/wiki/United_States_v._Wong_Kim_Ark).
**Why's everyone talking about this now?**
Trump noted [in an interview](
https://www.axios.com/trump-birthright-citizenship-executive-order-0cf4285a-16c6-48f2-a933-bd71fd72ea82.html) that he wants to prevent the children of people who aren't US citizens who are born on US soil from automatically becoming US citizens themselves.
>* "It was always told to me that you needed a constitutional amendment. Guess what? You don't," Trump said, declaring he can do it by executive order.
>* When told that's very much in dispute, Trump replied: "You can definitely do it with an Act of Congress. But now they're saying I can do it just with an executive order."
>* "We're the only country in the world where a person comes in and has a baby, and the baby is essentially a citizen of the United States ... with all of those benefits," Trump continued. "It's ridiculous. It's ridiculous. And it has to end."
>* "It's in the process. It'll happen ... with an executive order."
**Is that right?**
Not even close.
The problem, at least as far as Trump is concerned, is that he can't actually do that. Changing a constitutional amendment is *hard*. He's *claimed* it just requires an executive order, but you can't overturn the Constitution by executive order and so he's shit out of luck. (If you don't believe me, you can at least believe [Paul Ryan](
https://edition.cnn.com/2018/10/30/politics/birthright-citizenship-executive-order-trump-paul-ryan/index.html), or any of [these eleven legal experts](
https://www.vox.com/2018/10/30/18042638/trump-birthright-citizenship-14th-amendment-legal-experts). If you think this is a bad idea, I'd urge you to consider how you'd feel if a given President felt he could overturn the First, Second or Fifth Amendments with a single, unregulated stroke of the pen, and then get back to me. Hell, what if a President felt that he could overturn the Twenty-Second Amendment and do away with presidential term limits entirely?) It's also important to note Trump's sneaky little lie:
>We're the only country in the world where a person comes in and has a baby, and the baby is essentially a citizen of the United States ... with all of those benefits
Yes, it is true that the USA is the only country in the world where a person is (not essentially but *actually and completely*) a citizen of the United States, but only because it'd be pretty strange if it were the case that being born in France, Rwanda or Equatorial Guinea could grant you US citizenship. About thirty countries, including Brazil and Canada, also have unrestricted *jus soli* citizenship. The USA is rare, perhaps, but by no means unique in that regard.
This also butts heads with another weird little quirk of US citizenship: if you're a US citizen, by *jus soli* or *jus sanguinis*, [you have to pay taxes to the US *even if you're not in the country*.](
http://time.com/money/4298634/expat-expatriate-taxes-us-myths/) There's only one other country that taxes non-resident citizens in this way (and it's Eritrea, so if you guessed that ahead of time I'm very impressed). This has led to the situation where people who were born in the USA to foreign parents -- say, an early birth while on holiday -- are citizens of and must legally pay taxes to a country that they haven't been to since (and [also register for the draft](
https://www.americansabroad.org/requirements-of-us-citizenship/)).
**Who told him he could do it?**
In the interview, Trump said, 'You can definitely do it with an Act of Congress. But now they're saying I can do it just with an executive order.' Who are *they*?
Well, no one knows as yet. The person to look out for is probably Trump's immigration *doyen* (read into that what you will), [Stephen Miller](
https://www.theatlantic.com/politics/archive/2018/06/stephen-miller-family-separation/563132/). Most of the big Trump immigration policies have come via Miller's office, including the Muslim travel ban(s), the separation of children from their parents at the border, discontinuation of funding to 'sanctuary cities', and The Wall™. *Politico* has noted that this is an idea that Miller has been [involved with previously in the Trump Administration](
https://www.politico.com/story/2018/10/30/trump-birthright-citizenship-949660), so several news outlets are suggesting his potential involvement. (This may become very interesting in the coming days, if the rumoured Trump post-election shakeup happens; if Miller *has* had a lot of influence on this policy decision, his continuance as one of the most prominent faces in the Trump White House may wax or wane depending on the result of the midterms.)
**So what's the big deal?**
I know, I know... at this point, 'Trump says he's going to do something he can't legally do' is a bit of a [dog-bites-man news story](
https://en.wikipedia.org/wiki/Man_bites_dog_(journalism\)), but this is coming only a week out from an extremely important mid-term election in which the Republicans are expected to lose the House (unlikely also the Senate, but the odds of that are still higher than people were giving Trump of winning in 2016, so who even knows at this point?). Tough talk on migrants riles up the Republican base, and Trump needs that turnout to have any chance of legislative victories in the two remaining years of his term.
This dovetails nicely with the migrant caravan that is currently moving through Mexico and heading towards the United States. Trump and other Republican higher-ups are using the opportunity to stoke fear into the hearts of voters, claiming -- incorrectly -- [that this is an invasion](
https://twitter.com/realDonaldTrump/status/1056919064906469376) (hyperbole), [that Democrats want an open border](
https://twitter.com/realDonaldTrump/status/1054354059535269888), [that there are gang members and Middle-Easterners using the caravan to sneak across the border](
https://twitter.com/realDonaldTrump/status/1054351078328885248) (no evidence), and that people crossing in the caravan are doing so illegally. It's the last that's the most insidious, especially given that [he tried to pull the same shit when it came to the child detention debacle earlier this year](
https://www.reddit.com/r/OutOfTheLoop/comments/8s3bfa/what_is_the_deal_with_the_kids_in_concentration/e0we6r5/); in short, the caravan are not behaving illegally *yet*. The expectation is that when they arrive in the USA, the vast majority of them will claim asylum from the dangerous conditions in their home countries, which is a right granted by the USA to anyone on the planet.
This push for fear with regards to the caravan is pretty much everywhere because it works to get Republican-leaning individuals incensed enough to take the time out of their days to head to the polls. (Voter engagement is expected to be one of the Democrats' biggest advantages in the midterms, which are not traditionally considered a particularly sexy election cycle.) However, notable breaks from the President's rhetoric include Fox News anchor Shep Smith, who said on Monday:
>There is no invasion. No one’s coming to get you. There’s nothing at all to worry about. But tomorrow is one week before the midterm election — which is what all of this is about.
There is likely no better summation of the context of the story than that.