In a major legal development, a federal judge in New Hampshire announced on Thursday that he will certify a class action lawsuit encompassing all children who could be affected by former President Donald Trump’s controversial executive order aimed at ending birthright citizenship in the United States.

The executive order, which seeks to deny automatic U.S. citizenship to children born on American soil to non-citizen parents, has sparked national outrage and legal challenges since its proposal. Civil rights groups argue that the order violates the 14th Amendment of the U.S. Constitution, which clearly states that “all persons born or naturalized in the United States…are citizens of the United States.”

Judge Michael Cartwright, who is overseeing the case, stated during Thursday’s hearing that the lawsuit meets the legal criteria for class action status. “This case raises fundamental constitutional questions that affect a wide and vulnerable group—newborn children who, under current law, are entitled to citizenship,” he said.

In addition to certifying the class, Judge Cartwright said he would issue a preliminary injunction to temporarily block enforcement of the executive order. “Until the matter is fully resolved in court, no child shall be denied their rightful citizenship based solely on the immigration status of their parents,” the judge ruled.

The Department of Justice is expected to appeal the decision, setting the stage for what could become a landmark case in U.S. constitutional law.

This ruling is seen as a significant setback for Trump’s immigration agenda and a potential turning point in the national debate over the rights of children born in the United States.