Trump’s executive order, signed in January, seeks to deny citizenship to children who are born to people who are living in the U.S. illegally or temporarily. It is part of the hard-line immigration agenda of the president, who has called birthright citizenship a “magnet for illegal immigration.”

Class actions let people facing a common problem band together in a single lawsuit to obtain nationwide relief.

The federal judge reignited the legal standoff over President Trump’s efforts to deny citizenship to children born to undocumented parents.