US President Donald Trump has said he would invoke the Insurrection Act if he determined there was an insurrection in Los Angeles, sparking questions over how far he is willing to go to use his authority to curb protests.

Asked by reporters in the Oval Office if he intended to invoke the Insurrection Act, a mechanism that would allow active duty military to employ lethal force against Americans, he said: “If there’s an insurrection, I would certainly invoke it. We’ll see.”

The US President has branded the LA protesters “professional agitators and insurrectionists.”

The Insurrection Act allows the US President to use US military forces domestically to quell unrest, rebellion, or enforce federal law under specific conditions.

It was last used in 1992 by former US president George H.W. Bush to send the National Guard to LA amid riots in the city after the acquittal of four white police officers over the beating of Rodney King, America’s ABC News reports.

Mr Trump’s decision to federalise the National Guard and deploy Marines to the streets of Los Angeles is an unprecedented departure from long-held protocol.

Mr Trump has said the National Guard will stay in Los Angeles “until there’s no danger.”

Military experts said the Trump administration had “thrown out the playbook” with its extraordinary response to the anti-ICE protests that will see almost 5000 soldiers deployed to Los Angeles in the coming days.

For the first time in more than three decades, members of the United States Marine Corp have been deployed to quell violence on the streets of America.

They have joined 4000 troops mobilised when the President federalised the National Guard against the wishes of California’s Governor Gavin Newsom who warned the move risked inciting violence instead of stopping it.

Gov Newsom has slammed the President’s actions as that of a power-hungry dictator using the unrest to expand his executive powers.

It is the first time a President has federalised the National Guard without the consent of the state governor in more than 60 years.

The last President to do so was Lyndon Johnson in 1965 who invoked the authority in order to have troops protect civil rights advocates in the historic Selma to Montgomery march.

George HW Bush’s invoking of the Insurrection Act to mobilise the National Guard in response to the Rodney King riots came at the request of the Governor and Mayor after days of widespread carnage that resulted in dozens of deaths and hundreds of injuries.

In that instance, 2000 soldiers and 1500 Marines were deployed to bring order to the battered city.

The President’s response is a stark contrast to the January 6 riots in Washington DC when Trump supporters stormed the Capitol, injuring more than 150 police officers.

He later described January 6 as a “day of love” and went on to pardon many of those convicted over their participation in the violence.

In his first term, Mr Trump raised the idea of deploying troops in the wake up upheaval caused by the death of George Floyd at the hands of police however he didn’t follow through.

For the President, the chaos unfolding in LA is a welcome reprieve in a week when his public breakup with Elon Musk and criticism of his cornerstone spending legislation dominated the headlines.

It helps drive the Republican narrative that the Democrats are a party of chaos and lawlessness while the GOP is a pillar of strength, law and order.

Gov Newsom said the Marines were being used as political pawns.

He has already launched legal action over the National Guard decision and intends to do the same for the Marine deployment – however it may already be too late for LA.