Miller, the architect of some of Trump’s hard-line immigration ideas, told Fox News, “we’re looking at all legal options” regarding the practice known as birthright citizenship.

Many legal scholars exclude people in the U.S. on a temporary basis or in the country illegally from a key provision in the 14th Amendment of the U.S. Constitution, Miller said. It reads, “All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States.”

“That’s something that we have to look at,” Miller said.

Miller did not provide a timeline for when he expects to have a “correct” interpretation of the 14th Amendment.