Trump's Insurrection Act threat stands out against the law's long history

Donald Trump would not be the first president to invoke the Insurrection Act, as he has threatened, so that he can send U.S. military forces to Minnesota. The law, which allows presidents to use the military domestically, has been invoked on more than two dozen occasions — but rarely since the 20th Century's Civil Rights Movement. Federal forces typically are called to quell widespread violence that has broken out on the local level — before Washington's involvement and when local authorities ask for help.