Can Democrats prevent Trump from using his executive power to build a wall?

While some federal judges would defer to the president's power to declare an emergency, Goitein said, others would rule against him because of the unusual circumstances. Of the more than two dozen emergency declarations currently in effect, most are about economic sanctions against foreign actors or governments. A few in recent years have been domestic, like fighting swine flu. Goitein, an expert on emergency declarations, called the idea of Trump using one to build a wall because Congress won't give him the money "unprecedented."