Why Was the Law Necessary?
Arizona's illegal immigration law, passed in April 2010, would not have been necessary if the federal government had not put increased pressure on the state by beefing up border patrols in neighboring Texas and California.
Arizona Sen. John McCain introduced or co-sponsored immigration reform legislation in 2005 and 2007 and made it an important plank in his 2008 presidential campaign. Each time it failed to gain enough support. Meanwhile, the state has continued to wrestle with a growing number of illegal immigrants that now tops almost half a million.
Scope of the Law
The Arizona law, SB 1070, essentially does three things. First, it gives law enforcement the ability to question people about their residency status if they have a "reasonable suspicion" they are in the country illegally. It also cracks down on U.S. residents who knowingly transport or escort illegal aliens into the state. Finally, it makes it more difficult for businesses to employ undocumented immigrants.
New Police Powers
The most controversial aspect of the new law, however, is the additional enforcement powers granted police officers. Although Arizona's state residents overwhelmingly supported the law by a ratio of 2:1, opponents outside the state are applying attributes to it that don't exist. For example, many opponents are under the mistaken belief that police officers can just randomly stop people on the street if they think they might be an illegal alien. The truth is, officers can only question people who have been stopped for other potential violations. This aspect of the law isn't without precedence. In Pennsylvania, for example, officers can cite a driver for not wearing a seat belt, but only after they've been stopped for a moving violation. This punches a large hole in the theory propagated by pro-amnesty advocates that the new law will "distract" police officers from fighting crime (as though illegal entry into the U.S. weren't a crime). All this law does is allow police officers to question suspects about their immigration status, detain them until it's cleared up and/or charge them if they cannot produce documents validating their legal residency. Once the charges are filed, the suspect is then turned over to immigration authorities for further action, including deportment.
Racial Profiling
Opponents of the new law also believe that it will encourage racial profiling. While the possibility for this is admittedly high, illegal border crossings and the criminal and economic impacts on the state are the problems this law aims to arrest. Certainly non-Latino illegals reside in the state (and when discovered, they too should be questioned and charged), but the illegal residents from Mexico and Latin America are the ones causing the most problems for Arizonans. Nothing in the law gives police any more of a profiling incentive than they had before. Prior to the existence of this law, officers could notify the federal Immigration & Naturalization Service of a potentially undocumented resident, but could only hope the INS would be able to do something about it. Given the scope of the problem in the state and the limited resources available to the agency, however, more would fall through the cracks than not. Because the federal government abdicated its responsibility to safeguard the people of Arizona so blatantly, Arizona's lawmakers commandeered this responsibility by giving police officers the authority to act as an additional layer of security.
Presidential Irony
In his push to appease the Democrats' liberal base and get out the minority vote in a tough election year, President Barack Obama has expressed helplessness and even criticized Arizona for passing what he called "irresponsible" legislation. While he would have his supporters believe that the only way to solve the illegal immigration problem in Arizona is to grant all existing illegals amnesty and make it easier -- not harded -- to gain entry into the U.S., the reality is that, thanks to Congress' inaction, the president alone has the authority to increase enforcement of existing laws.
In other words, despite his innocent expression, shrugged shoulders and protestations to the contrary, Obama could have done something about Arizona's illegal immigration problem early on in his presidency. All he had to do was allocate more resources to patrolling the border in the Grand Canyon State. Trouble is, it was more politically expedient for him to put pressure on Arizona's resources, force the state to take action, then use the decision as a fulcrum for his own liberal agenda.

