Why is Trump trying to deploy the National Guard to US cities?

President Donald Trump’s deployment of the National Guard into several US cities has drawn a round of legal challenges by state and local officials.

Trump argues the use of federal troops is necessary to quell violence in Democratic-controlled cities, crack down on crime and support his deportation initiatives.

But several Democratic governors have pushed back, saying the deployments are unnecessary and risk escalating tensions.

Illinois filed a lawsuit on Monday asking a judge to block the deployment of troops to Chicago, while a federal judge on Sunday temporarily blocked the deployment of National Guard members from Texas and California to Portland, Oregon.

As the legal battles continue, here’s what to know about the National Guard:

The National Guard consists of primarily state-based troops that typically respond to issues like natural disasters or large protests.

All 50 US states, the District of Columbia, and the territories of Guam, Puerto Rico, and the US Virgin Islands have their own contingent of National Guard troops. Those troops also can be deployed abroad, and some units specialise in fighting wildfires or securing the US border.

Though the National Guard ultimately reports to the Department of Defence, and the president can federalise troops in certain circumstances, requests for its support typically start at a local level.

The governor of a state makes the call to activate National Guard troops during an emergency, and can request additional help from the president or other states.

National Guard troops have limited power, however. They do not enforce the law, or make arrests, seizures, or searches. And a law called the Posse Comitatus Act limits the power of the federal government to use military force for domestic matters.

Trump has tried to circumvent the normal process for deploying the National Guard several times now.

In June, he took control of the California National Guard to respond to protests against immigration raids in Los Angeles, even though California Governor Gavin Newsom objected. California filed two lawsuits against the Trump administration.

One lawsuit challenged Trump’s seizure of the National Guard, but an appeals court ultimately ruled in favour of the president. In a second lawsuit, a federal judge found that Trump’s use of the National Guard troops in Los Angeles violated the Posse Comitatus Act.

This summer, hundreds of National Guard troops arrived in Washington, DC because of what he called a “situation of complete and total lawlessness.” Trump cited homelessness and crime rates as justification.

Trump has now authorised the deployment of 300 National Guard to Chicago following immigration protests, particularly outside detention facilities. Governor JB Pritzker, a Democrat, alleged Trump is trying to “manufacture a crisis” and has filed a lawsuit.

This week, Trump attempted to deploy the National Guard to Portland, Oregon, before a federal judge temporarily blocked the action late Sunday night.

A little-known provision of US military law governs the president’s authority to deploy the National Guard on his own. But up until now, presidents rarely used it.

10 US Code § 12406 allows the president to call National Guard troops from any state into service if the US is “invaded or is in danger of invasion by a foreign nation,” or “there is a rebellion or danger of a rebellion” against the US government.

Trump invoked this law to federalise 2,000 National Guard troops in June in order to support ICE missions.

Defence Secretary Pete Hegseth also cited the law in a memo deploying 200 members of the Oregon National Guard into federal service on 28 September.

“We’re very confident in the president’s legal authority to do this,” White House press secretary Karoline Leavitt told reporters on 6 October. “And we’re very confident we will win on the merits of the law.”

Trump is again seeking to use the National Guard to respond to demonstrations, after protests near an ICE building in Portland over the weekend.

Federal officers, including with the Department of Homeland Security and Customs and Border Patrol agency, clashed with demonstrators who opposed Trump’s mass deportation initiative.

The Portland Police Bureau said it arrested two people on 4 October who engaged “in aggressive behaviour toward each other in the street” and refused to follow orders. One person was in possession of bear spray and a collapsable baton.

Oregon Public Broadcasting reported that federal law enforcement fired tear gas and smoke canisters to break up the protest and made several arrests.

Trump has claimed the city is “burning down,” but Oregon Governor Tina Kotek, a Democrat, said “there is no insurrection in Portland, no threat to national security.”

The Trump administration has moved to send 200 California National Guard troops to neighboring Oregon to respond to the protests.

But US District Judge Karin Immergut, who Trump appointed during his first term, has temporarily blocked his action in a pair of back-to-back rulings.

On Saturday, Judge Immergut blocked Trump from federalising the Oregon National Guard. “This is a nation of constitutional law, not martial law,” she wrote in her ruling.

The next day, she issued a temporary restraining order against him deploying California’s National Guard in Portland instead.

The Trump administration is expected to appeal.