In an interview published on Tuesday by Axios, President Donald Trump said he was preparing an executive order to end birthright citizenship in the United States.

That proposal harks back to a time when white supremacy was enshrined by law, and it may be the administration’s most direct assault yet on our democracy.

When the U.S. Constitution was ratified in 1788, it made no reference to the qualifications for citizenship, except for the provision that authorized Congress to regulate naturalization. However, the Constitution implicitly denied citizenship to enslaved Black Americans by treating them as property rather than people. Under the Fugitive Slave Clause, slaves who escaped to free states could not become free citizens, but instead would be “delivered up on Claim of the Party to whom [their] Service or Labour may be due.”

In 1857, the U.S. Supreme Court went even further in enshrining, by law, a white supremacist vision of citizenship. In Dred Scott v. Sandford, widely regarded as the worst decision in the Court’s history, Chief Justice Roger Taney ruled that Black Americans—including free Black Americans—“were not intended to be included, under the word ‘citizens’ in the Constitution, and can therefore claim none of the rights and privileges which that instrument provides for and secures to citizens of the United States.” Because Black people were not citizens, Taney reasoned, they had “no rights which the white man was bound to respect.”

Dred Scott was one of the factors that led to the Civil War. In the final days of that conflict, Congress passed the 13th Amendment to abolish slavery. But in the immediate aftermath of the war, many jurisdictions in the South passed laws known as the Black Codes, designed to return newly freed Black Americans to enslavement-like conditions. Congressional Republicans recognized that another constitutional amendment was necessary to codify the outcome of the Civil War. Hence, the Reconstruction Congress passed the 14th Amendment. Ratified in 1868, that amendment 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.”

The 14th Amendment changed everything. As with so much else in U.S. legal history, the courageous pursuit of dignity, justice, and equality by Black Americans enshrined new freedoms and rights for all people in this country. The 14th Amendment reversed Dred Scott, yes, but it didn’t stop there. In supplying the definition of citizenship that the original Constitution lacked, the 14th Amendment didn’t just say who could be citizens, but who were in fact citizens: anyone naturalized or born in the United States. For this reason, as Sherrilyn Ifill, president of the NAACP Legal Defense Fund, has written: “Efforts to undo birthright citizenship undermine the foundation of Black—and indeed all—civil rights.”

This is what makes the proposed executive order to eliminate birthright citizenship so chilling. The 14th Amendment is the legal basis for realizing the ideal of the United States as an egalitarian and pluralistic democracy; it is this ideal that the president and his allies want to erase. This proposed executive order is not about immigration policy for non-citizens. It is about preserving the power of white citizens in the face of an increasingly diverse electorate by pretending that a significant number of predominantly Black and brown citizens are, in fact, not citizens at all. To achieve that end, the president would deny citizenship to some people born in the United States—the first time any president had attempted to do so since the Civil War.

This proposal would be breaking the law. The language of the 14th Amendment unequivocally says that anyone born in the United States is a U.S. citizen. Consistent with that plain language, Congress has expressly recognized that persons born in the United States are citizens at birth. Executive orders cannot override constitutional amendments; not even a new law can do that. No matter what the president’s lawyers say, the Constitution can only be changed by amendment. Amendments can only be proposed by a constitutional convention called by two-thirds of state legislatures (which has never happened), or by a two-thirds majority in both houses of Congress. The proposed amendment would then need to be approved by three-quarters of the states.

That’s a reassuring fact, but it doesn’t mean we can simply ignore the proposed executive order. The president’s mere willingness to flout the 14th Amendment is an indication of how far we have traveled into uncharted territory. If the last 21 months have taught us anything, it is that we cannot take our laws and rights for granted. The president has made his intentions clear; we remain silent at our peril.

And the “we” means all of us. For decades, adherents of the conservative legal movement have insisted they are wary of government overreach, and that the plain text of the Constitution must be strictly enforced. If that was anything more than a convenient talking point, now is the time to speak up. If you don’t, if we all don’t, it may be too late. If the president can override the plain text of the Constitution with an executive order, we are a country ruled not by law but by whim.