Some union leaders and Democratic U.S. House members criticized the arrest as an effort to intimidate protesters and criminalize peaceful demonstrations.

Immigrants are now so heavily represented in many unions that even when nearly all have legal work status, deportations are keenly felt because many workers have undocumented family members.

Los Angeles police swiftly enforced a downtown curfew, making arrests moments after it took effect, while deploying officers on horseback and using crowd control projectiles to break up a group of hun...