President Donald Trump’s executive order to end so-called birthright citizenship for babies of undocumented immigrants was blocked indefinitely by a fourth federal judge, handing the administration another legal setback and signaling an uphill constitutional fight.

The 14th Amendment was ratified in 1868, after the Civil War, with the intention of granting full citizenship rights to freed African American slaves; its birthright citizenship clause has since been interpreted to include all U.S.-born children, regardless of parental immigration status.

BOSTON (AP) — A federal judge in Boston on Thursday blocked President Donald Trump’s executive order that would end birthright citizenship for the children of parents who are in the U.S. illegally, becoming the fourth judge to do so.