The National Emergencies Act of 1976 allows the president to trigger emergency powers conferred on him not by me, but by Congress. It has been in place in various forms for more than 150 years. It confers powers on a president that I think go too far, such as confiscating private businesses, etc. In this case, involving building a border barrier of some kind, that is a uniquely federal governmental responsibility. The president can use the law to undertake such a project, and it can be challenged in the courts or overturned by a joint resolution of Congress. He needs...