Since taking office, President Donald Trump has sparked controversy over and over with his use of the National Guard - primarily state-based troops that typically respond to issues like natural disasters or large protests.
But Trump has sought to use them very differently: deployments to major US cities where residents protest his political agenda, particularly immigration policy.
Trump argues the National Guard is necessary to quell violence in Democratic-controlled cities, support his deportation initiatives, and crack down on crime. But some former military officials, several Democratic governors, and federal judges have expressed concern that this is a major overreach and risks politicising the military.
The latest clash occurred in early October when Trump tried to send National Guard troops to Portland, Oregon, where protesters rallied outside a US Immigration and Customs Enforcement (ICE) building to protest its immigration enforcement tactics. A judge has temporarily blocked the move and the case is ongoing.
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 National Guard support typically start at the local level.
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.
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.
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.
And this week, Trump attempted to deploy the National Guard to Portland, Oregon, before a federal judge temporarily blocked the action late Sunday night.
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.
Oregon Governor Tina Kotek, a Democrat, said 'there is no insurrection in Portland, no threat to national security.'
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 Trump administration is expected to appeal.