By ADAM LIPTAK
 
In ruling yesterday that the United States must provide Mexicans on death row with a fresh opportunity to argue that their convictions should be overturned, the World Court set itself on a collision course with American courts and officials.

Over several days last year, lawyers from the State and Justice Departments mounted a vigorous defense to Mexico's claims, imploring the court not to intrude into the American criminal justice system.

Mexico's demands, which included a request that the court void all the convictions, represented, American lawyers said in a court filing, "an unjustified, unwise and ultimately unacceptable intrusion into the United States criminal justice system."

The court did not go as far as Mexico wanted. Though it found violations of the convention in 51 cases, it declined to void any convictions and insisted only on "review and reconsideration" of the claims made by the death row inmates. The question is whether that middle ground will be applied by American courts.

Treaties are, under the Constitution, "the supreme law of the land." But American courts have been quite reluctant to apply rulings of international tribunals.

The court ruled, moreover, that American courts may not rely on a doctrine known as procedural default to decline to hear arguments not raised at trial. That is at odds with recent death penalty jurisprudence in the United States, much of it based on a 1996 federal law that limits what kinds of arguments may be made if they were not raised early on.

The international court also rejected the United States' contention that it may comply with the ruling by allowing death row inmates to raise claims during clemency proceedings before state governors. Only reconsiderations by courts count, the international court said.

The court also made a prospective suggestion, saying that a sensible way to avoid Vienna Convention problems is to alert foreigners to their rights by adding a sentence to the standard Miranda warning.

The first case in which the ruling on Wednesday may have an impact is that of Osbaldo Torres, who is to be executed May 18 in Oklahoma for his role in the murder of a couple in front of their children during a burglary in 1993. Mr. Torres has exhausted his appeals.

Mark Henricksen, a lawyer for Mr. Torres, said he expected the state to grant a hearing. "We're hopeful that Oklahoma will honor the decision" of the international court, he said. "In our view it's an unappealable order."

The state's attorney general, Drew Edmondson, suggested in a statement yesterday that further judicial proceedings were indeed in order. "It is now up to Mr. Torres to convince a court that assistance from the Mexican government could have changed the outcome of his trial," he said.

But Mr. Edmondson added that there was no evidence that Mr. Torres's case was prejudiced by his inability to meet with Mexican officials. "This office is ready to respond to any attempt to delay justice," he said.

Mexico has a legal assistance program in the United States because, its diplomats say, Mexicans are often bewildered by American procedures and many speak poor English. Mexican lawyers told the court that in the cases when consular protection was allowed, life sentences had been more likely than death sentences.

Sandra L. Babcock, one of the lawyers who represented Mexico in The Hague, said the Torres case may mark a turning point.

"This is going to be a great case to see if the United States is going to comply with this decision in good faith," she said.