President Donald Trump threatened on social media Thursday to invoke the Insurrection Act to stop resistance to ICE activity in Minnesota.

United States presidents have used the act about 30 times in the past, according to NPR. The most recent was in 1992. That year, President George H.W. Bush invoked the law to quell riots in Los Angeles after four police officers were acquitted in the beating of Rodney King.

Trump has talked before about using the law to support immigration enforcement.

For perspective on the law, MPR News host Nina Moini talked with University of Minnesota law professor Ilan Wurman, who specializes in Constitutional law and presidential power.