The Supreme Court's rejection Monday of an Arizona law that demands voters prove they are citizens before casting ballots threatens to scuttle similar state laws nationwide.

The justices decided 7-2 to uphold a lower court's ruling that rejected the law, which requires residents to show "satisfactory evidence" of citizenship when using a registration form produced under the federal motor-voter registration law.

States still could demand voters produce such documentation if they get permission from the federal Election Assistance Commission -- created in response to Florida's ballot-counting troubles during the 2000 presidential election -- or a federal court ruling overturning the panel's decision.

But the commission has been in limbo since late 2010, when it last had a quorum. All four seats currently are vacant.

Arizona Secretary of State Ken Bennett said he was "disheartened" by the high court's decision but will ask the commission to back the state's plan. If the panel refuses, he said he will "plan to pursue further litigation."

The ruling is likely to have implications in other states with similarly strict voter ID laws, including Alabama, Georgia, Kansas and Tennessee -- though it's uncertain if the high court's ruling means those states would have to completely rewrite or tweak their laws. Several other states also considering such laws.

Other decisions by the justices on Monday:

» Justices said drugmakers can be sued over deals with competitors that keep low-cost generic medicines off the market.

The justices decided 5-3 to allow the government to inspect and challenge what it calls "pay for delay" deals or "reverse payment settlements." Such deals occur when generic companies file a challenge with the Food and Drug Administration to the patents that give brand-name drugs a 20-year monopoly. The big companies sometimes reach a compromise that allows the generic company to sell its cheaper copycat drug in a few years -- but years before the drug's patent would expire. The deal often includes a large cash payment from the brand-name company to the generic drugmaker.

Justice Samuel Alito did not take part in the case, giving no reason.

» The Supreme Court said prosecutors can use a person's silence against him if it comes before he is told of his right to remain silent.

The 5-4 ruling comes in the Texas case of Genovevo Salinas, who was convicted of a 1992 murder. During police questioning, and before he was arrested or read his Miranda rights, Salinas refused to tell investigators if a shotgun he had access to would match up with the murder weapon.

Prosecutors used his silence on that question in convicting him of murder, saying it helped demonstrate his guilt. Salinas appealed, saying his Fifth Amendment rights to stay silent should have kept his silence from being used against him in court. Texas courts disagreed, saying pre-Miranda silence is not protected by the Constitution. The high court upheld that decision.

» Justices said a jury should have the final say on facts that can trigger mandatory minimum sentences in criminal trials.

In a 5-4 decision, the court overturned the sentencing of Allen Alleyne, who was convicted of robbery and firearm possession in Richmond, Va. The jury said his accomplice didn't brandish a weapon, but the judge said he did -- raising Alleyne's minimum sentence from five to seven years.

Alleyne's lawyers say the brandishing decision should have been the jury's, and the justices agreed, sending the case back for resentencing.

» The court also ruled 5-4 that lawyers may not obtain personal information from state driver's license records to recruit clients for lawsuits.

The case involved a complaint by South Carolina residents who objected to solicitations from lawyers to join a lawsuit against car dealers. Justice Anthony Kennedy said in his majority opinions that a lawyer's solicitation of clients is prohibited by a federal privacy law intended to shield motor vehicle records.

The high court left it to lower courts to determine whether letters sent by the lawyers were predominantly efforts to recruit clients.

– Wire service reports contributed

The courts in recent years have upheld several state laws that have strengthened rules requiring voters to show identification before casting ballots -- most noteworthy a landmark 6-3 Supreme Court decision in 2008 that upheld a photo ID requirement in Indiana.

But because the Arizona law centered around proof of citizenship -- not just a photo ID -- many legal analysts said the law presented justices with significantly different circumstances than other voting ID cases.

Arizona voters approved the law in a 2004 referendum. A group of Arizona residents, American Indian tribes and civil-rights groups sued the state over the law. The 9th U.S. Circuit Court of Appeals ruled in their favor, saying the citizenship requirement conflicted with the motor-voter law, which was drafted partly to make it easier for residents to register to vote. Arizona appealed, but the high court agreed with the lower court's decision.

Federal law "precludes Arizona from requiring a federal form applicant to submit information beyond that required by the form itself," said Justice Antonia Scalia, who wrote for the court's majority.

Justices Clarence Thomas and Samuel Alito dissented from the court's ruling.

Defenders of the citizenship requirement said it is a valuable tool to combat voter fraud. But the law's critics argued it imposed an unfair burden on residents and threatened to disenfranchise minorities, the poor and others.

Wendy Weiser of the Brennan Center for Justice at the New York University School of Law called the ruling a "huge victory" for voters.

"We applaud the Supreme Court for confirming Congress' power to protect the right to vote in federal elections," said Weiser, who runs Brennan's Democracy Program.

The Supreme Court also is expected this month to announce a ruling on another voting-rights case that could end a landmark Civil Rights-era law designed to combat discriminatory voting practices nationwide.

Shelby County, Ala., is challenging a provision in the 1965 Voting Rights Act that requires all or parts of 16 states, mostly in the South, to get approval from the Justice Department or a federal court before making changes in the way they hold elections.

Shelby County -- a mostly white suburb of Birmingham -- says it no longer should be forced to live under oversight from Washington because it has made significant progress in combating voter discrimination. Supporters of the law say it has been among the nation's most effective tools to eradicate racial discrimination in voting.