In an interview with WVLK in Lexington, KY, Speaker of the House Paul Ryan (R-WI01) rejected the idea that President Donald Trump could end “birthright citizenship” – automatic citizenship for those born in the United States regardless of the parents’ status – with an executive order.

“Well, you obviously cannot do that. You cannot end birthright citizenship with an executive order,” Ryan was quoted as saying in a report by Politico. “As a conservative, I’m a believer in following the plain text of the Constitution, and I think in this case the 14th Amendment is pretty clear, and that would involve a very, very lengthy constitutional process. But where we obviously totally agree with the president is getting at the root issue here, which is unchecked illegal immigration.”

Some Republican lawmakers from the anti-immigration wing of the party, including President Donald Trump, believe that the 14th Amendment was not intended to cover children born here of illegal immigrants. The first section of the 14th Amendment says:

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. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

The amendment was ratified as part of the Reconstruction Era after the Civil War and the citizenship clause was written to overturn the Dred Scott decision which denied citizenship to African American slaves. However, because of the wording of the text, the amendment has since been interpreted to cover all who are born in the United States.

Trump’s case for abolishing birthright citizenship via executive order is even more difficult given Congress’ authority over naturalization under Article I, section 8 of the constitution. Republicans had objected to President Barack Obama’s changes to immigration policy without Congress, and Trump’s plan to use an executive order in such a drastic fashion would be a major reversal for congressional Republicans if they supported the president on this issue.

The statement by Trump in an interview for HBO about ending “birthright citizenship” comes less than a week before the midterm elections. Immigration has become a major issue in the election as a large caravan of potential asylum seekers marches through Mexico towards the U.S. border.

In Wisconsin, immigration has been a point of difference between state Sen. Leah Vukmir (R-Brookfield) and U.S. Sen. Tammy Baldwin (D-WI). Baldwin generally has been for less restrictive immigration policy and rejects Trump’s call for building a solid wall to secure the U.S. southern border. Vukmir has made supporting the president’s policies a cornerstone of her campaign.

According to multiple media reports, Vukmir said she supports citizenship for those born of parents who are here legally but she  did not indicate her position on the president’s ability to end birthright citizenship. “Illegal immigrants are taking advantage of America’s generosity and I applaud President Trump’s courageous leadership to fix our immigration crisis,” Vukmir said.

Ryan said believing in the Constitution as written meant Trump’s authority was limited.

“I think the smarter, faster solution here is to crack down on illegal immigration and obliviously support doing that,” Ryan said. “But I’m a believer in the Constitution, I believe in interpreting the Constitution as written, and that means you can’t so something like this via executive order.”