(CNN) Attorney George Conway, the husband of White House counselor Kellyanne Conway, called President Donald Trump's proposal to end birthright citizenship "unconstitutional" in a Washington Post op-ed he co-wrote Tuesday.

"Sometimes the Constitution's text is plain as day and bars what politicians seek to do. That's the case with President Trump's proposal to end 'birthright citizenship' through an executive order," Conway writes, along with Obama-era US Solicitor General Neal Katyal. The duo argues this is due to the 14th Amendment.

"Such a move would be unconstitutional and would certainly be challenged. And the challengers would undoubtedly win," they added.

George Conway's stance contrasted with that of his wife. Kellyanne Conway told reporters Tuesday that "there are constitutional scholars that say the 14th Amendment has been misinterpreted, and, actually, the Supreme Court has never gave a solid opinion on this."

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