President Donald Trump is aiming to eliminate the long-standing birthright citizenship law in the U.S. Constitution with a case due before the U.S. Supreme Court — but an expert said Tuesday his argument is sorely lacking.

Earlier this year, the high court dodged making a definitive ruling, but this time justices will consider the constitutionality of Trump's executive order concerning the constitutional rule that anybody born in the U.S. is American.

Writing for SCOTUSBlog, immigration law and policy expert César Cuauhtémoc García Hernández walked through the administration's argument, citing 19th-century sources such as former Justice Joseph Story. The problem, he pointed out, is that using Story to justify a reframing of the 14th Amendment "misses key nuance from the past."

"To support the administration’s claim that Trump’s executive order merely seeks to enforce the clause’s original meaning, [Solicitor General D. John] Sauer relies on multiple sources that provide a much more complicated assessment of jurisdiction than the government admits, including six citations to the influential associate justice of the Supreme Court Joseph Story. Sauer argues that '[a] substantial body of historical evidence confirms' Trump’s view of the citizenship clause, repeatedly referencing Story," Hernández writes.

First, Story died in 1845. That is "more than 20 years before Congress drafted the 14th Amendment." So, the idea that Story could have years' worth of writings or opinions on a law that wasn't even on the books ignores historical realities.

Still, Sauer cites Story at least six times in his argument, including one that "misreads Story’s claim" entirely.

Second, he quotes a passage from Story’s 1834 book, Commentaries on the Conflict of Laws, Foreign and Domestic, Sauer declares that "children born to parents who were in transit or temporarily in a country do not receive citizenship." He quotes Story correctly, but he "misreads" the claim, says Hernández.

"Story is clear that he is describing his view of what the law should be rather than making an uncontested claim about what it is," the immigration law expert continues.

The quote Sauer uses has a disclaimer after it. "Story explains that the exclusion upon which Sauer relies 'would seem to be' a 'reasonable qualification,' but, as he notes in the following sentence, this qualification had not been 'universally established.'"

And it's one of the six quotes that Sauer tries to use to justify Trump's argument.

Hernández closes by noting that every court in which the case has been heard has decided against the administration. Not one has agreed that it is legal.

Read the full column here.