The New Civil War (War Between the States), circa 2010

Wait a minute! Something's illogical here: Arizona passes a tough, new law aimed at uncovering and deporting illegal aliens. Los Angeles, CA, USA, disliking the Arizona law very intensely, states it is going to declare economic war (stop doing convention business) with Arizona. A sovereign US county is going to war with a sovereign US state on behalf of foreign nationals??!! Never mind "Doctors Without Borders"; is LA saying we now have "Nations Without Borders?" Please, someone, help me with my confusion.