When can a president deploy the National Guard?

Dozens of people have been arrested in Los Angeles after days of violent protests, which erupted following immigration raids.

US President Donald Trump deployed 2,000 National Guard troops to the city, triggering a political row. He also condemned what he called "violent, insurrectionist mobs".

Vehicles have been set on fire and there have been reports of looting in affected areas of America's second largest city.

The protests began on Friday after it emerged Immigration Customs Enforcement (ICE) officers were carrying out raids in areas of the city with prominent Latino populations.

Raids have stepped up after Trump returned to the White House and pledged to crack down on illegal immigration.

The BBC's US partner, CBS News, reported that recent operations took place in the Westlake district as well as in Paramount, south of LA - where the population is more than 82% Hispanic.

There were also reports of an ICE raid at a Home Depot shop in Paramount, which officials told the BBC were false.

ICE later told CBS that 44 unauthorised immigrants were arrested in a single operation at a job site on Friday. Another 77 were also arrested in the greater LA area on the same day.

The protests have been largely limited to downtown LA, which has been declared an "unlawful assembly" area by police after days of clashes.

• Vehicles were set alight on Sunday, and police accused protesters of using incendiary devices against horse patrols. Meanwhile, officers in riot gear have used flash-bang grenades and pepper spray to subdue crowds. The unrest temporarily brought the 101 freeway to a halt, and there were reports of looting
• The downtown Federal Building has become a flashpoint after it emerged that ICE detainees were allegedly being held there. On Saturday, ICE accused "over 1,000 rioters" of surrounding and attacking the building
• A Home Depot shop in Paramount, roughly 20 miles (32 km) south of downtown LA, has become another key protest site. Tear gas and flash-bangs were deployed against protesters who also gathered on Saturday, and armed National Guard troops guarded a nearby business park on Sunday
• The Los Angeles Police Department (LAPD) said it made 29 arrests on Saturday. A further 27 people were arrested on Sunday
• Separately, about 60 people were arrested and three officers injured following unrest in San Francisco on Sunday, police there said

Elsewhere in the sprawling city of LA, life continues as normal - and some areas were closed off over the weekend for the LA Pride parade.

On Saturday, Trump deployed 2,000 National Guard members to the Los Angeles area, triggering a political row with state politicians.

The National Guard acts as a hybrid entity that serves both state and federal interests. Typically, a state's force is activated at the request of the governor.

Trump circumvented that step by invoking a rarely-used federal law, arguing that the protests constituted "a form of rebellion against the authority of the government of the United States".

This is reportedly the first time the National Guard has been activated without request of the state's governor since 1965.

The move has been condemned by California Governor Gavin Newsom and LA Mayor Karen Bass, who said they believed local police could handle the situation.

Newsom accused Trump of an "illegal" act that was "putting fuel on this fire", and has threatened to sue.

The role of the National Guard is to protect federal agents, including ICE and Department of Homeland Security (DHS) personnel, as they carry out their duties.

The troops will not be conducting their own immigration raids or performing regular policing - which remains the role of the (LAPD).

The law generally prohibits domestic use of federal troops for civilian law enforcement, outside of some exceptions like the Insurrection Act.

Although Trump has threatened to invoke that act in the past, during the Black Lives Matter protests of 2020, for example, he has not done so here.

Trump's allies have defended his decision to mobilise the National Guard. Defence Secretary Pete Hegseth also said active-duty US marines stationed at nearby Camp Pendleton would be sent if needed and were on "high alert".

The recent raids are part of the president's aim to enact the "biggest deportation operation" in US history. Los Angeles, where over one-third of the population is born outside of the US, has been a key target for operations.

In early May, ICE announced it had arrested 239 undocumented migrants during a week-long operation in the LA area, as overall arrests and deportations lagged behind Trump's expectations.

The following month, the White House increased its goal for ICE officials to make at least 3,000 arrests per day.

Authorities have expanded their search increasingly to include workplaces such as restaurants and retail shops.

The ambitious deportation campaign has included removing migrants to a mega-prison in El Salvador, including at least one who was in the US legally. Many of Trump's actions have been met by legal challenges.