Last night, President Trump restated his desire to build a border wall, despite Congress’ refusal to appropriate funding for it. Fortunately, he did not declare a “national emergency,” as he had previously threatened to do. But administration officials indicate that option remains on the table if Congress refuses to give in to Trump, as is highly likely. The claim that emergency authority can be used to build the wall and seize property through the power of eminent domain is highly dubious. If the President succeeds, it would set a dangerous precedent.