It’s more nuanced than building a wall to stop immigrants from entering the country, but President Trump’s new rule limiting the people who can become Americans to those who won’t need public assistance is a lot more significant.

This is a change that has the potential to be so vast that one official who is implementing it likens it to an addendum on the Statue of Liberty. Here’s what Ken Cuccinelli, acting director of U.S. Citizenship and Immigration Services, said when asked about it on NPR.

“Would you also agree that Emma Lazarus’s words etched on the Statue of Liberty, ‘Give me your tired, your poor,’ are also part of the American ethos?' ” host Rachel Martin asked.

“They certainly are,” Cuccinelli replied. “Give me your tired and your poor who can stand up on their own two feet and who will not become a public charge.”

On this, he and immigration rights advocates agree: This rule is almost unquantifiable in how it could reshape immigration. It could allow wealthier people, largely from whiter countries, to become Americans and limit or even block many poor people, largely from Mexico, Central America and Asia, from becoming naturalized citizens.

It’s such a significant change that not even most Republicans in Congress supported similar ideas. Two years ago, Trump endorsed a bill from two of the most conservative lawmakers to limit legal immigration by switching to a merit-based system over having families sponsor relatives. Then he brought it up in his State of the Union address. It went nowhere in a Republican-controlled Congress.

Because although Trump and his fellow Republicans generally agree that they want to crack down on illegal immigration, significantly changing legal immigration, as this rule does, takes it too far for many lawmakers.

This new rule broadly expands the definition of “public charge,” a definition the government has long used to weigh whether legal immigrants can continue on the path to citizenship or whether they will be a burden on society and should essentially be kicked out.

When the rule takes effect in October, people can be denied a green card if they have used, have qualified for or are likely ever to use food stamps, housing assistance or Medicaid.

As The Washington Post’s Abigail Hauslohner, Nick Miroff, Maria Sacchetti and Tracy Jan report, immigration experts and public officials estimate that will reshape the entire field of applicants. Some data points on this, to the best it can be grasped:

  • About 400,000 people this year will apply for a new immigration status with the United States, and nearly all of them will be subject to this rule.
  • Nearly 70 percent of green-card holders could have had marks against them with this new rule if it were in place when they applied. (Although officials say the rule is not retroactive, this is a good indicator of the kinds of people who are applying for green cards now).
  • An untold number of immigrants who apply in the future could be determined by the federal government to be “likely” to become a societal burden. As The Post reports, this new rule states that having “a medical condition” that would interfere with work or school, “financial liabilities” or insufficient English-language skills would be enough to be rejected.
  • An untold number may never apply for fear of being rejected.

What’s more, immigration advocates say that hundreds of thousands of immigrants are likely to stop requesting federal help to avoid having their immigration application status denied. The Kaiser Family Foundation says that 7.6 million children could be at risk of losing their public health-care benefits because they live with someone who is not a citizen and could be kicked out because they use these public benefits.

The Trump administration is unwavering.

“This is part of President Trump’s keeping his promises,” Cuccinelli told NPR. “This is not new or a surprise.”

And he’s right. Trump hasn’t let something like Congress, or a Republican Party that has no appetite for limiting legal immigration, get in his way.

He tried to get Congress to fund his wall on the U.S.-Mexico border. It didn’t, so he went around it by declaring a national emergency and taking money from the military.

Trump tried to get Congress to limit legal immigration. It didn’t. So now he’s implementing a rule that, more than any wall he campaigned on and kept the government closed for, will vastly change who Americans let into America. It’s an idea so radical that he has had to go it alone without leaders in his own party.