NATIONWIDE -- President Donald Trump, speaking from the Rose Garden on June 1, threated to invoke the Insurrection Act in order to quell nationwide protests.

“If a city or state refuses to take the actions that are necessary to defend the life and property of their residents, then I will deploy the United States military and quickly solve the problem for them,” Trump said.

The statement came after Trump earlier in the day blasted some governors as “weak” and urged them to activate the National Guard and make more arrests.

What is the Insurrection Act and how would it be applied? It turns out it’s a very old federal law that has only been used a little more than a handful of times.

The Insurrection Act of 1807 grants the president of the United States the authority to deploy military troops within the country in certain circumstances. Those circumstances include rebellion, insurrection and civil disorder.

In addition to the armed forces, the act permits the president to deploy the National Guard.

The act has been invoked sparingly, most recently in 1992 by George H. W. Bush at the behest of California in response to the Los Angeles riots.

Prior to invocation, the president must issue a proclamation ordering insurgents to immediately disperse.

Specifically, the act permits the president to call into service the armed forces and National Guard under the following circumstances:

• When requested by a state's legislature, or governor if the legislature cannot be convened, to address an insurrection against that state;
• To address an insurrection, in any state, which makes it impracticable to enforce the law (§ 252); or
• to address an insurrection, domestic violence, unlawful combination or conspiracy, in any state, which results in the deprivation of Constitutionally-secured rights, and where the state is unable, fails, or refuses to protect said rights

Following Hurricane Katrina, Congress amended the act, extending it to natural disasters, terrorist attacks and public health emergencies.

The act was probably most famously used in the 1950s to enforce desegregation and in the 1960s in response to riots in Detroit.

Typically, the act is invoked at the behest of governors, but that may not be a necessity. If Trump were to invoke the act, it would likely be challenged legally and protested by governors as overreach.

Click the video link above to watch our interview with Stephen Vladeck, a constitutional law professor at UT Austin.

The Associated Press contributed to this report.