The AP has a pretty good backgrounder here on the federal government's lawsuit against Arizona's new immigration-enforcement law, spelling out why the feds think the law is unconstitutional -- and why supporters say the government is missing the point.
Homeland Security officials say the government cannot possibly find, arrest and deport everyone who is here illegally. And trying to do so would also upset a balance crafted by Congress that takes into account humanitarian interests and foreign relations.
But proponents of the Arizona solution insist that's no reason not to try. And they say the state's toughest-in-the-nation law is a reasonable way to start.