There’s been a lot of noise lately about whether children born on U.S. soil automatically get citizenship. The conversation roared back into the spotlight when details emerged about Secretary of State Marco Rubio’s old legal brief, back when he was merely a senator fending off birther accusations in 2016. In that filing, he seemed to champion the traditional reading of the Constitution—that pretty much everyone born here is labeled a citizen.

Today, President Trump’s administration is pushing an order that restricts birthright privileges, outraging immigration activists. But what about Rubio, who once submitted a court paper that spelled out how the 14th Amendment granted citizenship to nearly all newborns, no matter their parents’ immigration status? He’s now in the thick of enforcing the new executive order. And according to official statements, he’s aligned with the president in trying to rein in birthright citizenship. That is quite the reversal.

Critics condemn the pivot as blatant opportunism, given that Rubio’s parents were immigrants who only became citizens after he was born. Outspoken law professors say that in 2016, Rubio laid out a concise legal stance for the inclusive view of birthright citizenship—and they argue that opposing that principle now might create legal vulnerabilities for the White House’s push. Federal courts are indeed mulling the president’s order, which aims to block automatic citizenship for babies born to noncitizen parents with temporary or unauthorized status.

Behind the scenes, the administration insists there’s nothing contradictory about Rubio’s stance. Supporters say times have changed, the border is more porous, and they accuse left-wing lawyers of letting foreign nationals exploit the system. They point to the Constitution’s requirement that one must be “subject to the jurisdiction” of the United States for the 14th Amendment to apply. People who are here illegally, they argue, are not fully under U.S. jurisdiction.

Those more moderate on this issue suspect it’s not so simple. They note that if Rubio’s logic from 2016 stood the test of time, it would strongly undercut the White House’s new policy. Then there’s the question of political fallout: Will Republicans risk throwing support behind a measure that will almost certainly face a Supreme Court showdown? The administration’s legal team contends that prior rulings never truly settled the matter of undocumented or temporary visa holders. Meanwhile, states and organizations are embroiled in lawsuits over eligibility for passports, child benefits, and more.

The White House’s fans say cracking down on birthright citizenship will dissuade people from crossing the border illegally, and it’s an idea that resonates with many who believe an open-door approach is unsustainable. The administration, energized by success in other immigration battles, is prepared to fight. They argue it’s time to modernize the rules so that unscrupulous foreigners can’t show up, have a child, and then use that newborn’s citizenship status as a lifeline for staying in the country indefinitely.

Amid all this, Rubio’s name keeps surfacing. Some see him as a walking contradiction, while others say he’s simply recognized the urgent need to fix an abused system. He’s chosen to brush aside any mention of the old brief, focusing instead on praising the president’s unwavering push to strengthen immigration laws. Observers see the bigger theme: a broad realignment in the party, moving away from the consensus that used to define them on immigration issues.

If the administration prevails, birthright citizenship could be reined in significantly. Yet success isn’t guaranteed, given the weighty constitutional questions at play. The Supreme Court may ultimately decide. As for Rubio, he’ll either be praised for adaptability or pinned as a figure of hypocrisy. The American people, meanwhile, watch to see whether the centuries-old tradition of citizenship by birth will remain intact—or if this White House will rewrite the rules for a new era.