The firestorm over President Donald Trump’s declaration of a national emergency to build a wall on the U.S.-Mexico border ignited with a fury Friday, as several groups vowed to sue the administration over what they’ve decried as an end-run around the Constitution.

Trump announced during a Friday press conference that he would declare a national emergency to begin construction of a wall. Much of the $8 billion dedicated for the project would come from diverting funds appropriated for other purposes, including the Defense Department’s military construction projects.