What are the rules of force for National Guardsmen, Marines at LA protests?

Their weapons are not loaded with ammunition, a U.S. official said.

The Marines and the National Guard personnel deployed amid the protests in to Los Angeles will operate under the same rules of force and will not be engaging crowds unless necessary, according to two U.S. officials.

That means they are tasked with protecting federal buildings and federal personnel only -- they will not patrol U.S. streets or try to detain protesters to assist police, the officials said.

While all the troops are carrying weapons, their guns will not have ammunition loaded in the chamber, officials said, but will carry ammunition as part of their regular uniforms that can be used in the rare case of needed self-defense.

They will not use rubber bullets or pepper spray, either, they said.

The officials noted these rules would change if President Donald Trump invokes the Insurrection Act, which he has not done.

The rules of force the personnel are operating under call for them to de-escalate the situation as much as possible.

"The arrival of federal military forces in Los Angeles -- absent clear coordination -- presents a significant logistical and operational challenge for those of us charged with safeguarding this city," Los Angeles Police Department Chief Jim McDonnell said in a statement.

"The Los Angeles Police Department, alongside our mutual aid partners, has decades of experience managing large-scale public demonstrations, and we remain confident in our ability to do so professionally and effectively," he continued. "That said, our top priority is the safety of both the public and the officers on the ground. We are urging open and continuous lines of communication between all agencies to prevent confusion, avoid escalation, and ensure a coordinated, lawful, and orderly response during this critical time."

Retired Air Force Brig. Gen. Thomas Edmonds, a former vice commander of the Michigan Air National Guard, told ABC News, "If I were an on-scene commander in my previous life as a [National] Guard officer, I would immediately demand clarification, for my people's sake. I would be saying, so what, when do we use deadly force?"

Edmonds said it appears the military is "defining the mission as non-law enforcement."

"But they're putting them with law enforcement personnel as their 'protection.' And I don't see the distinction there between if I'm engaged in protecting a federal officer [or] federal building, [and if] I'm engaged in enforcing the law."

The Marines and Guard troops being sent to Los Angeles are being led by Army Maj. Gen. Scott Sherman, who is deputy commander of U.S. Army North, officials said.

In total, there are 4,800 troops operating under Title 10 status: 4100 of them National Guard soldiers and 700 active-duty Marines.

Title 10 of the U.S. Code contains a provision that allows the president to call on federal service members when there "is a rebellion or danger of rebellion against the authority of the Government of the United States" or when "the President is unable with the regular forces to execute the laws of the United States."

The deployment of the 700 Marines was to ensure "adequate numbers of forces to provide continuous coverage" of the area, according to U.S. Northern Command.

The deployed force is known as "Task Force 51" and officials insist the troops have been trained in de-escalation, crowd control, and standing rules for the use of force.

ABC News' Alex Stone contributed to this report.