ANALYSIS: Can President Trump legally deploy US troops to US cities?

President Donald Trump walks in Lafayette Park to visit outside St. John's Church across from the White House Monday, June 1, 2020, in Washington. Part of the church was set on fire during protests on Sunday night. (AP Photo/Patrick Semansky)
President Donald Trump walks in Lafayette Park to visit outside St. John's Church across from the White House Monday, June 1, 2020, in Washington. Part of the church was set on fire during protests on Sunday night. (AP Photo/Patrick Semansky) (Copyright 2020 The Associated Press. All rights reserved.)

(CNN)President Donald Trump threatened Monday night to invoke the Insurrection Act of 1807 law and take the unusual step of deploying active-duty US soldiers to police US streets.

While Trump claims the move would break up anti-fascists, or Antifa, who he says are organizing violent riots that have led to looting, it would also effectively squelch peaceful protests for racial justice after the death last week of a black man, George Floyd, after a police officer used lethal force during a stop.

That would be a remarkable turn on the law, which was most notably used in the 1950s to enforce desegregation. And later, in the 1960s, to address riots in Detroit.

According to the Congressional Research Service, it hasn't been invoked since 1992 during the riots in Los Angeles that followed the acquittal of four white police officers in the beating of Rodney King. Now-Attorney General William Barr was actually attorney general back then, too, under former President George H.W. Bush.

Congress amended the law after Hurricane Katrina in 2006 to give more clarity about its use during natural disasters, but dropped some of those changes a year later after objections by state governors who did not want to cede their authority.

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But Trump said Monday that if governors did not act to his liking, he would call up the military.