President Trump says he’s planning to end birthright citizenship “with an executive order.” He can’t, as several experts have pointed out.

Yet those critics who say the rule can change only through a constitutional amendment, such as House Speaker Paul Ryan (R-Wis.) and the Atlantic’s Garrett Epps, also go too far. The 14th Amendment’s citizenship clause, as attorneys George T. Conway III and Neal Katyal correctly note, was an effort to define previously enslaved African Americans as U.S. citizens. But when they acknowledge that “it is Congress, not the president, who is in the driver’s seat when it comes to immigration,” they fail to note that it can steer birthright citizenship policies in a new direction.

The 14th Amendment’s citizenship clause did not even address, much less resolve, the question of citizenship for the U.S.-born children of undocumented immigrants. As we discuss in our 1985 book, “Citizenship Without Consent: Illegal Aliens in the American Polity,” the federal government was not then restricting immigration. (The U.S. slave trade was banned by this time, but that was not immigration in any sense we think of it today.) Although the clause states, “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,” Congress and courts were left to work out the full meaning of the words, “and subject to the jurisdiction thereof.”

The Constitution empowers Congress, the Article I branch of government, to establish rules for naturalization. Congress has consistently exercised that authority to design citizenship policies, and federal courts have consistently supported this: Native Americans born within tribes, sometimes also termed “domestic dependent nations,” were found not to possess birthright citizenship in the 1884 Supreme Court holding in Elk v. Wilkins. There, the high court acknowledged that the plaintiff was “subject, as residents of the states, to all the burdens of government” but yet, as a Native American, was not considered part “of any political community, nor entitled to any of the rights, privileges, or immunities of citizens of the United States.” Regardless of how retrogressive that reasoning sounds now, it was only after passage of the Indian Citizenship Act of 1924 that all Native Americans were recognized as citizens by the federal government.

But until Michael Anton, a former Trump aide with no formal legal background, asserted, earlier this year in a Washington Post op-ed, that the president could, by executive order, tell federal agencies that children of unauthorized immigrants are not citizens, no one, to our knowledge, has ever seriously suggested citizenship rules could be altered by executive action. And with good reason; this would clearly violate the Constitution’s separation of powers.

There are, to be sure, legitimate issues about whether the current U.S. practice of universal birthright citizenship is the most desirable policy. Most of the developed nations in the world set some limits on birthright citizenship, frequently requiring one parent to be a citizen to confer citizenship on a child. Countries such as the United Kingdom, Ireland and India have newly established such limits in recent decades. We are not, ourselves, in full agreement on what policy is best. Rogers Smith sees no pressing need to alter the current policy and believes that, because congressional committees have repeatedly considered but refused to adopt revisions to it in the three decades since we first wrote, this perception is widely shared. Peter Schuck maintains that the courts do not treat such legislative inaction as equivalent to an affirmative policy decision, and that a sound policy would not grant citizenship immediately at birth, but would grant retroactive birthright citizenship to such children when they have resided here for a certain number of years and have attended a certain number of years in American schools.

Since his campaign, Trump has increasingly sought to mobilize political support by fomenting heightened fear and hostility toward immigrants legal and illegal. In the most recent instance, he insists that our national security is threatened by the efforts of a few thousand Central American migrants to reach our southern border, flamboyantly deploying troops to appear tough on immigration — we both reject this posturing and demonization.

Trump is either being wishfully or willfully provocative when he says, “now they’re saying I can" do away with birthright citizenship "just with an executive order.” But he wasn’t wrong to state that “You can definitely do it with an Act of Congress.” Those who argue otherwise are either evaluating the language of the citizenship clause without sufficient care, or they’re engaging in wishful thinking of their own.