Cavel International Inc. closed its plant in DeKalb, Ill., last year after a federal appeals court upheld the ban. The company urged the justices to step in to allow the facility to reopen. The court did not comment on its order Monday.

The plant was the last horse slaughterhouse in the United States. About 40,000 to 60,000 horses were there annually, and most of the meat was shipped to be eaten by diners overseas.

Two other U.S. plants, both in Texas, also closed in 2007.

The unanimous decision came in the cases of Shawqi Omar, taken into custody in Iraq for allegedly assisting a terrorist network, and Mohammad Munaf, whose death sentence by an Iraqi court was recently overturned. Munaf has been accused in Iraq of setting up the 2005 kidnapping of three Romanian journalists.

Held by the U.S. military at Camp Cropper near Baghdad International Airport, both men are Sunni Muslims who say they will be tortured if turned over to the Iraqi government.

Chief Justice John Roberts wrote that U.S. courts are not allowed to intervene in an ongoing foreign criminal proceeding and "pass judgment on its legitimacy."

The justices ruled that basic protections do extend to American citizens held overseas by U.S. military operating as part of a multinational force. At the same time, however, the court said those protections provide Omar and Munaf with no legal relief.

The Bush administration argued that U.S. courts lack authority to review the claims of Munaf and Omar because they are held abroad by a multinational force, of which the United States is only a part.

Nations including Iraq have criminal jurisdiction over those within their borders, said the Justice Department solicitor general's office.

Arrested in 2004 by U.S. soldiers at his home in Baghdad, Omar was to have been transferred to Iraqi courts for trial, but a U.S. district court blocked the move.

In a case that is continuing, an Iraqi court recently reversed Munaf's death sentence.

In a 6-3 decision, the justices said that Anup Engquist must be a member of a class targeted for discrimination in order to bring a claim.

The case revolves around an 8-year-old Supreme Court decision. In that case in 2000, the justices ruled that a person may assert an equal protection claim as a "class of one" rather than on the usual grounds of racial discrimination against an entire group.

Writing for the majority, Chief Justice John Roberts said that the "class of one" theory does not apply in the public employment context, where the government has greater leeway in dealings with its employees.

Born in India, Engquist worked at a laboratory operated by the Oregon Department of Agriculture. She says that after she complained about a colleague who allegedly harassed her, the man and a superior eliminated her position. A jury subsequently ruled in Engquist's favor.

Nine federal appeals courts have ruled that public employee claims similar to Engquist's can go forward.

In a 5-2 decision, the court rejected a claim by nine female students at Randolph College — formerly Randolph-Macon Woman's College — that promotional materials and other publications promised them four years at an all-female institution.

Chief Justice Leroy R. Hassell Sr. wrote in the majority opinion that the court could find nothing in marketing materials promising the school would stay single-sex.

The decision affirmed Lynchburg Circuit Judge J. Leyburn Mosby Jr.'s dismissal of the lawsuit. The dissenting justices said dismissal was premature, and the students were entitled to a trial.

"We're all very relieved," Randolph College President John Klein said. "This seemingly endless litigation is now over." Klein said a student and some staff members rang the college bell to celebrate.

"We hope now we can focus on the students who are here and who want to come here," he said. The board voted in September 2006 to begin admitting men to the school, beginning last fall.

Drugmaker Merck & Co. doesn't have to cover medical-monitoring expenses for Vioxx users who aren't claiming injury from the recalled painkiller, the New Jersey Supreme Court ruled.

Phyllis Sinclair and Joseph Murray sued Merck in 2004, seeking to have the company fund a medical-screening program for U.S. consumers who took Vioxx for at least six weeks. New Jersey law requires plaintiffs to show physical injury, the Supreme Court said in an opinion.

In addition to punitive damages, the suit sought to have the Whitehouse Station, N. J.-based company fund a screening program to provide diagnostic tests for each member of the proposed class and a follow-up with an epidemiologist.

The 5-1 ruling by the state's highest court means a class-action lawsuit by people who used the once-popular painkiller will be dismissed. One justice did not participate.

The lawsuit was filed by Vioxx users who claim they have no immediate symptoms but that use of the drug gives them a greater risk of developing illness. So they want diagnostic testing to uncover any hidden or developing problems.

Because they aren't claiming they have an injury, they aren't eligible for the settlement Merck announced in November. Merck agreed to pay $4.85 billion to settle thousands of U.S. personal injury lawsuits involving a heart attack, stroke or death. Some 45,000 eligible claimants had initiated enrollment as of March 31.

The high court said that since the Vioxx users in the case don't claim injury, they "cannot satisfy the definition of harm" in seeking medical monitoring under the state's Product Liability Act.

In dissent, Justice Virginia A. Long argued that the law encompassed a broad definition of harm, and includes the concept that an "increased risk of injury that creates a need for medical surveillance" is a recognizable harm.