A federal judge temporarily blocked President Trump’s executive order declaring that children born on U.S. soil to undocumented immigrants would no longer be treated as citizens. The judge, John Coughenour, sided with states that had sued Trump arguing that the president’s order violated the 14th Amendment. “This is a blatantly unconstitutional order,” he said today.

“Frankly,” Judge Coughenour, a Reagan appointee, added, “I have difficulty understanding how a member of the bar would state unequivocally that this is a constitutional order. It just boggles my mind.”

The order to end birthright citizenship, set to take effect on Feb. 20, also extends to babies born to mothers who are in the country legally but temporarily, such as tourists, university students or temporary workers.

The judge’s injunction, which lasts two weeks, marks the beginning of what will almost certainly be a long battle between the new administration and the courts over Trump’s ambitious second-term agenda.