Marco Rubio once wrote a tightly argued defense of a constitutional right to birthright citizenship that President Donald Trump is now seeking to undo through an executive order.

Now secretary of state, Rubio was a senator running for president in 2016 when he made the case that the Constitution bestowed citizenship on basically all children born in the United States after a fringe candidate for president challenged his ability to seek the White House, reported the New York Times.

“There’s no reason why the argument he put to work in 2016 couldn’t be put to work today against the Trump executive order,” said Temple University law professor Peter J. Spiro, who added that Rubio's filing was a “powerful, succinct statement of why the 14th Amendment has been interpreted to cover almost all children born in the United States, regardless of parental immigration status.”

Rubio submitted the brief in response to a federal lawsuit filed in Arkansas by independent presidential candidate David Librace, who argued that the then-senator was ineligible to run for president because he was not a "natural born citizen" because he had been born in 1971 to Cuban immigrants who would not become citizens until four years later.

"The arguments Mr. Rubio made in his brief were broader than they needed to be to win his case," wrote correspondent Adam Liptak for the Times. "He addressed, for instance, not only the Constitution’s presidential eligibility clause but also the provision of the 14th Amendment on birthright citizenship."

"He went on to say that the amendment, the common law on which it was based and the leading Supreme Court precedent all confirmed that 'persons born in the United States to foreign parents (who were not diplomats or hostile, occupying enemies) were citizens of the United States by virtue of their birth,'" Liptak added.

By contrast, Trump contends that children born to parents who are in the U.S. temporarily or unlawfully are not automatically granted citizenship because they are not “subject to the jurisdiction” of the United States, and the president's order has been held up by legal challenges since it was issued.

“Particularly weak is the administration’s attempt to distinguish among legally present noncitizens,” Spiro said. “By trying to exclude the children of so-called nonimmigrants — including student visa holders and temporary workers — the administration loses the argument that it’s only targeting those who are here in violation of the law.”

Rubio's filing nearly a decade ago reflected the long-held convention wisdom about the 14th Amendment's meaning, but a State Department spokesman did not address the arguments set forth in that brief when asked to comment on it.

“It’s absurd the NYT is even wasting time digging around for decade-old made-up stories,” Tommy Pigott, a State Department spokesman. “[The secretary of state is] 100 percent aligned with President Trump’s agenda.”