A state of emergency is usually justified by a political leader or a government if existing powers are not enough to combat a crisis. In the US, Congress also passed numerous laws in previous centuries, giving the President additional emergency powers in the event of a military, economic or labour market crisis. Some of these have not only been archived, but are also currently in force. After the adoption of the National Emergencies Act in 1976, the President is still free to decide when to declare a state of emergency. During an emergency, both houses of Congress must meet every six months and discuss whether a vote on terminating the emergency should be conducted. The emergency decree expires automatically after one year, unless it is renewed by the President.
Overall, very little is mentioned in the constitution about the powers held by the President or Congress within the framework of an emergency. An emergency is referred to briefly in Article I and II. The powers held by the President in an extreme situation in a very important area can be derived from Article II of the constitution as well as from the position of the President as commander-in-chief of the US army. The constitution also contains very little by way of concrete details on the system of checks and balances for the emergency powers. In certain cases, the Supreme Court had to decide on the extent of the emergency powers. Some powers were granted, others not – at the same time, the Supreme Court has frequently tried to avoid judging on cases. This gives the President considerable scope during an emergency.
If President Trump declares a state of emergency in order to build a wall along the Mexican border – which many observers by no means deem pressing enough to justify such a step – he would therefore appropriate considerably more power. He could, for example, deploy the army to build the wall. Fundamentally, however, hurdles are also in place. Besides the fact that some republicans are concerned about possible reactions in their constituencies, or that the emergency option would also set a precedence in the future with a US Democratic president, proceedings would probably be instituted against the emergency before the US Supreme Court. Although the Supreme Court has taken very different decisions in the past on emergency measures, it is not clear whether Trump will get his plans through despite a preponderance of conservative Supreme Court judges. He would then take the risk that the Supreme Court would view the emergency as being unjustified and that the Democrats would then try to initiate impeachment proceedings against him. Ultimately, it therefore seems very unlikely that Trump will actually invoke the emergency option.