The justices, by a 7-2 vote, said states can give trial judges discretion to prevent someone from acting as his own lawyer if they are concerned that the trial could turn into a farce.

The decision comes in the case of an Indiana man who was convicted of attempted murder and other charges in 2005 for a shooting six years earlier at an Indianapolis department store.

Ahmad Edwards was initially found to be schizophrenic and suffering from delusions and spent most of the five years after the shooting in state psychiatric facilities. But by 2005, he was judged competent to stand trial.

Edwards asked to represent himself. A judge denied the request because he was concerned that Edwards' trial would not be fair. Edwards, represented by a lawyer, was convicted anyway and sentenced to 30 years in prison.

He appealed, and Indiana courts agreed that his right to represent himself had been violated, citing a U.S. high court decision from 1993. The courts overturned his conviction and ordered a new trial.

The Texas Court of Criminal Appeals on Wednesday ruled that Routier should be allowed to conduct DNA testing on blood stains, flakes of dried blood and hairs found at the crime scene.

Routier's previously appeals to the court had been denied, but state law allows for post-conviction DNA testing in some cases. Routier has maintained that she is innocent of the murders.

Routier was accused in the slayings of the young boys, Damon and Devon, but was only tried and convicted in the death of Damon. She has maintained that an intruder at the family's home killed them.

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.