I am in the position of supporting a state's rights issue position, the which I almost never do. However...
California has "sanctuary" laws. State Senate Bill 54 prohibits state law enforcement from using state resources to assist ICE in enforcement actions against non-violent illegal immigrants. And Los Angeles also has its own sanctuary law, extending the same prohibition to city resources. Federal courts have upheld the right of cities and states to make such laws.
By tradition, when state and federal laws conflict on social issues like immigration or marijuana, the feds mostly let state law take precedence. The feds will go in and make arrests, but only if they have a compelling reason in a particular case. Lack of local cooperation makes it a bit dangerous for federal officers to operate in these communities, and it's also a states' rights issue. So illegal immigrants have had de facto amnesty there for a long time, and many are longstanding, well-integrated community members who work jobs, own homes, and pay taxes.
The Trump admin's position is that sanctuary laws are an illegal obstruction of federal authority. They've dispatched ICE in large numbers and full military kit to arrest nonviolent illegal immigrants living under California's sanctuary. They've been aggressive and deceptive, going around in masks and sometimes plainclothes, grabbing people en masse, without explanation, from homes and places of work. My brother's neighbor got arrested by armed ICE officers who busted down his door and pointed guns at his wife and kids.
Californians predictably hate this. It violates all norms and tradition, and they're watching friends, neighbors, and colleagues who've lived here peacefully for decades get kidnapped by armed and masked men who race up in military vehicles and then try to make a quick getaway. People are protesting, trying to block vehicles, in some cases throwing things at ICE agents. ICE agents have responded with tear gas, nonlethal munitions, and physical force.
There are hotheads on both sides. During one ICE raid, a mother got out of her car to see what was going on, and an ICE agent shot her in the face with a tear gas canister and sent her to the hospital. There were no protesters present yet in this case. Protesters have burned some cars and given Fox News some great propaganda visuals by waving Mexican flags near disorderly scenes.
Trump and Stephen Miller seem to be using this to actively provoke armed confrontation with (and to seek excuses to use military force against) blue states. They have declared L.A. protesters to be in armed insurrection against the US government and have called in the California National Guard to pacify them. The legality of this is dubious. The posse comitatus act allows the president to call upon the national guard to put down an insurrection, but not for domestic law enforcement. (Historically, claims of insurrection were used during Reconstruction to justify martial law under posse comitatus in the post-Civil War South.)
All of this comes against the backdrop of generally cruel and illegal enforcement actions against immigrants by the administration, including wrongful arrests of citizens and legal residents, deporting immigrants without due process, denying habeas corpus rights, throwing immigrants in foreign prisons, jailing people who legally apply for entry at the border, revoking student visas to punish universities, revoking visas on flimsy grounds like traffic citations, etc. Even many conservatives are saying stuff like, "we thought they would deport criminals, not moms." White House deputy chief of staff Stephen Miller was reportedly irate when ICE officials similarly expressed that they thought the mission was going after criminals. That is not the White House's mission, apparently.
Eerie parallels here to past fights over states' rights that escalated into full-fledged civil conflicts.
