The Supreme Court is preparing to hear oral arguments over the constitutionality of S.B. 1070, a controversial immigration law passed by Arizona in 2010. The law is considered to be one of the harshest of its kind in the country, and liberals argue that it encourages discrimination against Latinos. Conservatives, on the other hand, say the law is necessary to plug holes in a broken immigration system. The case is prompting an emotional, polarized reaction, the likes of which were last seen just a month ago, when the court weighed whether to strike down President Obama's health care law. And the court's decision in Arizona v. United States, expected in June, will likely roil the presidential campaign only months before the November election. Here, a guide to its latest hot-button case:

Why is S.B. 1070 so controversial?
The law has numerous provisions that civil rights groups argue are unconstitutional. S.B. 1070 requires schools to check the immigration status of all students, from kindergarten through 12th grade; makes it a state crime for immigrants to leave home without their immigration documents; and bars undocumented immigrants from finding work in Arizona. Most controversially, the law requires police officers to demand identification papers from any suspect they stop if they have a "reasonable suspicion" that the person is an illegal immigrant. Critics say the provision, known as the "papers, please" section of the law, will unfairly target Latinos.

How does the law reduce illegal immigration?
Proponents of the law say its tough measures will make "life so difficult for illegal immigrants" that they'll choose to "self-deport," says Alan Gomez at USA Today. Furthermore, the law is supposed to discourage them from coming to Arizona in the first place.

What issue is the Supreme Court considering?
The court is not deciding whether S.B. 1070 violates civil rights. Instead, it must weigh the "long-established boundaries between the federal government and the states when it comes to immigration enforcement," says Julia Preston at The New York Times. The Obama administration is arguing that the Constitution enshrines the federal government's right to dictate immigration policy. Arizona says it was forced to act because the federal government has failed to secure the border, "resulting in about 400,000 illegal immigrants now living in the state," says Jim Malone at Voice of America.

How is the court expected to rule?
It's not clear. Scholars say court precedent alone suggests that the Obama administration will prevail, but court politics have become so intense that it's hard to predict which way the decision will go, says Gomez. The court's strong conservative bent has raised the "distinct possibility" that the justices "could uphold at least some of the Arizona law's contested sections," says Preston. Only last year, the court upheld a different Arizona immigration law that punished businesses "that knowingly hired illegal immigrants," says Gomez, possibly creating a roadmap to uphold S.B. 1070.

Will the court's decision have an impact beyond Arizona?
Yes. Since Arizona passed S.B. 1070 in 2010, five states — Alabama, Indiana, South Carolina, Utah, and Georgia — have passed copycat laws. If the court upholds the law, more states could follow suit, which would "create profound inconsistencies in policies between different states," and divide the country into areas that are "welcoming and unwelcoming" to immigrants, says Nathan Pippenger at The New Republic. On the other hand, if the court strikes down the law, it would likely "cool some of the enthusiasm for similar laws in state legislatures across the country." 

Will it affect the presidential race?
Definitely. Mitt Romney, the presumed GOP candidate, has publicly backed parts of S.B. 1070. The law is "especially popular with Republicans, who support it by 84 percent," says Josh Lederman at The Hill. However, the law is deeply unpopular with Latinos, "the fastest-growing voter bloc in the country," which could possibly hurt Romney's election chances. Democrats are already taking advantage of the split, with Senate Democrats saying they will propose legislation to invalidate S.B. 1070 if the court upholds it. 

And how will the court's decision affect Obama?
A decision to strike down the law would vindicate Obama, but it "could hurt him if it galvanizes conservatives" come November, says Lederman. Similarly, a ruling to "uphold the law could also energize his Democratic base and give the president another way to run against the Supreme Court in the fall." Obama has already given a preview of such a strategy in the fight over ObamaCare, suggesting that a decison to strike down health care would be a form of naked judicial activism. 

Sources: The HillThe New RepublicThe New York Times, USA Today, Voice of America, The Washington Post