When Donald Trump declared an emergency at the southern border of the United States, he mentioned the possibility of invoking the Insurrection Act of 1807. This archaic law was actually drawn up in 1792 when the United States was a very different country to the one Trump presides over today. The statute has been used by various White House incumbents on numerous occasions since, but critics argue that it is dangerously vague and in need of reform. So what exactly is the Insurrection Act, and why and when is it invoked?
Click through the following gallery and learn more about this centuries-old law and how it can be used.