The Supreme Court will conclude one of its most significant and controversial terms in decades by taking on one more issue that has divided the nation: Arizona’s crackdown on illegal immigrants.

The court’s final oral argument on Wednesday — Arizona v. United States — provides yet another chance for the justices to confront fundamental questions about the power of the federal government. And the rulings the court will issue between now and the end of June could dramatically alter the nation’s election-year landscape.

The court has considered President Obama’s health-care law, has taken its first look at the political redistricting battles being fought across the nation and will decide whether federal regulators still hold the authority to police the nation’s airwaves.

The Obama administration has moved aggressively against Arizona’s SB 1070, which directs law enforcement to play a much more active role in identifying illegal immigrants and makes it a crime for them to seek work. The administration has persuaded courts to put aside key parts of the law.

And, as with last month’s hearings on the health-care law, in the Arizona case the government is asking the court to recognize that the Constitution gives the federal government vast powers to confront national problems, such as illegal immigration.

Presumptive Republican presidential candidate Mitt Romney speaks at a rally in Arizona in front of their state flag on April 20. Romney’s tough stance against illegal immigration has angered some interest groups and is said to have cost him among increasingly influential Latino voters. (JOSHUA LOTT/REUTERS)

“As the framers understood, it is the national government that has the ultimate responsibility to regulate the treatment of aliens while on American soil, because it is the nation as a whole — not any single state — that must respond to the international consequences of such treatment,” Solicitor General Donald B. Verrilli Jr. told the court in the government’s brief.

Immigration is one of the nation’s thorniest political issues. Obama and his administration have been accused of not properly securing the nation’s borders and criticized for not delivering comprehensive immigration reform. Presumptive Republican presidential nominee Mitt Romney’s tough stance against illegal immigration has angered some interest groups and is said to have cost him among increasingly influential Latino voters.

And even as the pace of illegal immigration has slowed, it has left a changed picture of undocumented immigrants in the United States. According to the liberal Center for American Progress, 63 percent of illegal immigrants have been in the country for more than 10 years and more than 16.6 million people in the United States have at least one undocumented family member.

Tom Saenz, president and general counsel of the Mexican American Legal Defense and Education Fund, said that while the legal issues in Arizona v. United States “relate to the structure of government, it is still very much a civil rights case.”

Beyond Arizona

The decision will have implications well beyond Arizona. Several states have copied — and toughened — Arizona’s law, and more are considering such steps.

“This debate is not just about SB 1070,” Arizona Gov. Jan Brewer (R) said in a statement when the state filed its brief in the case. “Rather, it is for the constitutional principle that every state has a duty and obligation to protect its people, especially when the federal government has failed in upholding its core responsibilities.

“SB 1070 is Arizona’s way of saying ‘enough!’ ”

The Obama administration opposed Arizona’s efforts from the start, as it has similar laws passed in Alabama, Georgia, South Carolina, Utah and elsewhere.

“Arizona has adopted its own immigration policy, which focuses solely on maximum enforcement and pays no heed to the multifaceted judgments” that Congress intends for the executive branch to make, Verrilli wrote in the government’s brief. “For each State, and each locality, to set its own immigration policy in that fashion would wholly subvert Congress’s goal: a single, national approach.”

The Obama administration persuaded a federal judge and then the U.S. Court of Appeals for the 9th Circuit to keep four sections of the law from taking effect, and they will be at the heart of the Supreme Court’s review. Those sections:

●Require state and local law enforcement to verify the citizenship status of anyone stopped, detained or arrested when there is “reasonable suspicion” that the person is in the United States unlawfully.

●Authorize law enforcement officials to make and arrest without a warrant when an officer has “probable cause to believe . . . [t]he person to be arrested has committed any public offense that makes the person removable from the United States.”

●Make it a state crime to be in the United States unlawfully and require non-citizens to carry documents to prove they are legally in the country.

●Make it a state crime for a person who is not lawfully in the country to work or seek work. Federal law puts the burden on employers to verify the legality of those seeking work.

Familiar faces

The case before the court offers a rematch of the lawyers who last month argued the constitutionality of the Patient Protection and Affordable Care Act: Verrilli for the government and Paul D. Clement, president George W. Bush’s solicitor general, representing Arizona.

Clement’s brief opens with page after page of costs and crimes that have accompanied a wave of illegal immigration across Arizona’s borders: Schools, hospitals and jails are overtaxed. Home invasions related to drug smuggling and human trafficking have soared. “Incredibly,” Clement writes, the federal government has even posted signs warning travelers: “Danger — Public Warning — Travel Not Recommended.” “Active Drug and Human Smuggling Area.” “Visitors May Encounter Armed Criminals and Smuggling Vehicles Traveling at High Rates of Speed.”

Clement says SB 1070 is not imposing new immigration standards but merely directing its own officials to make sure federal laws are respected.

“Such cooperative law enforcement is the norm, not something that requires affirmative congressional authorization,” Clement writes.

Verrilli responds that the Arizona law’s “very design discards cooperation and embraces confrontation.”

He describes a complex federal policy of detaining and deporting illegal immigrants prioritized on criminal activity and other factors. The Department of Homeland Security receives funding to remove annually about 400,000 of the approximately 11 million people in the country illegally, he says, and it is up to federal officials — not Arizona’s — to decide who they should be.

And he says Arizona’s decision to impose criminal sanctions on those who seek work is an idea Congress debated and rejected in passing immigration legislation in 1986.

The Supreme Court in its previous term signaled that immigration enforcement is not solely the province of the federal government. In a 5 to 3 vote, it agreed that Arizona could revoke the business licenses of companies that knowingly employ undocumented workers.

The court in that case said Arizona was in line with an exception in the 1986 law that allows states leeway in the licensing of businesses, Chief Justice John G. Roberts Jr. wrote.

The same eight justices will hear Wednesday’s Arizona case — Justice Elena Kagan recused herself in both, presumably because of her work on the issue in her previous job as Obama’s solicitor general.

If they split evenly, the 9th Circuit’s injunction of those aspects of the Arizona law would stand and the larger issue of federal authority would need to wait for a challenge to one of the other states’ laws.

As with health care, the case has attracted a raft of amicus briefs. Sixteen states, including Virginia, are supporting Arizona; 11, including Maryland, say the federal government must play the dominant role in immigration.

The stance of each state follows less the number of immigrants within its borders and more the political party of its leadership.