In 1895, in his early 20s, Wong Kim Ark returned to the United States, the place of his birth.

He’d grown up in San Francisco, the son of Chinese immigrants, and was a cook by trade. His parents had returned to their own homeland in 1890, and he’d gone with them — but in the time since he’d established a transnational lifestyle.

He’d started a family in China, but repeatedly made trips back to the US to work. In fact, he’d just met his first child, conceived on an earlier trip, and gotten his wife pregnant with a second.

Such arrangements were not uncommon for Chinese-American men, as the Chinese population in the US was overwhelmingly male.

The US was in the grips of intense anti-Chinese sentiment, and Chinese immigration had been cut off in 1882. But since he’d been born in the US, he was able to return by showing the documents required by local customs officials, including testimony from white people that he was a US citizen.

Or at least that’s how it had worked for him before. In 1895, it was different.

Wong was denied entry by a stridently anti-Chinese customs collector, on the grounds that he was not in fact a US citizen, owing to his parents’ status as Chinese immigrants at the time of his birth. Then he was held on ships for months as he fought the case — with legal help from the “Six Companies,” a Chinese-American organization that had made a point of standing up for Chinese civil rights in thousands of court cases.

Eventually it was decided, on the basis of an earlier appeals-court precedent, that his US birth made him a citizen. But the US attorney general decided to push the issue further, and his case ended up at the Supreme Court.

That court’s ultimate decision is back in the spotlight now. In an interview released early this week, President Trump announced a plan to take on “birthright citizenship” via executive order.

This is the rule under which just about everyone born in the USA — including the children of illegal immigrants — is automatically granted citizenship, and the rule that Wong helped make US law.

It’s important to understand the situation Wong was born into. Between 1860 and 1880, the Chinese-American population tripled, topping 100,000 by the end of that period and concentrated largely in California. In 1868 a treaty explicitly welcomed these migrants — though they were not eligible for naturalization. And while Chinese-Americans made up small percentage of the overall American population, the tide shifted after repeated economic recessions, fueling a racist backlash.

In theory, Wong’s case posed a rather narrow question: Whether he was covered by the 14th Amendment clause granting citizenship to “All persons born or naturalized in the United States, and subject to the jurisdiction thereof.”

Today, most courts would carefully parse those words, check dictionaries as needed, consult legal texts to see if the phrase was a term of art, and perhaps read up on the legislative history as well, to see what the people who actually wrote the words intended to convey.

Back then, however, the Supreme Court took a different path. In a 6–2 ruling, it touched on the text and history of the actual amendment only lightly and decided to cement the definition of citizenship we’d inherited from English common law, where everyone born in the country is treated as a natural subject. The same rule had applied to whites in the US since the country’s founding, the Court said, and the amendment had extended the rule to everyone else.

This is how Wong got his citizenship. And it’s why birthright citizenship presents such an enormous hurdle for those that oppose it.

Opponents of birthright citizenship today aren’t trying to prevent legal immigrants from re-entering the country if they visit their homelands, though, or to exclude entire racial groups.

Rather, they primarily fear — quite sensibly — that immediately granting citizenship to the children of people who came here illegally serves as a magnet, or at least a reward, for crossing our borders without authorization.

Today’s immigration critics are also correct to point out that the 14th Amendment wasn’t written with illegal immigration in mind, as there were no immigration restrictions yet in 1868 when it was adopted. One imagines that if illegal immigration had been an issue at the time, the amendment would read quite differently, in a way that clearly gives Congress the ability to deny citizenship in cases where people broke the law to get it.

So, what does all of this actually mean for Trump’s planned order? If Congress passed a new law ending birthright citizenship, the courts would immediately hear challenges rooted in the 14th Amendment, with Wong Kim Ark a key precedent.

Today’s Supreme Court could certainly reconsider the issue and consult a wealth of evidence that the 1898 Court mostly ignored, including the debates surrounding the 14th Amendment. But there is strong evidence from those debates that the amendment was, in fact, meant to confer citizenship on virtually everyone born here, with just a handful of exceptions (such as the kids of foreign ambassadors).

There are respected legal scholars who disagree — advancing a theory that “jurisdiction” requires allegiance to and the consent of the US — but a challenge to birthright citizenship would require all five conservative justices to read the historical evidence in a very specific way and break with decades upon decades’ worth of precedent and standard practice.

Wong Kim Ark eventually returned to China for good. His legacy will remain a part of America for far, far longer.

Robert VerBruggen is a deputy managing editor of National Review