A United States Appeal Court on Friday refused to entertain a lawsuit that accused Royal Dutch Shell Plc of helping Nigerian authorities violently to suppress protests against oil exploration in the 1990s.

Specifically, the plaintiffs, families of seven Ogoni indigenes who were executed by the regime of the late General Sani Abacha, had accused the oil giant of violations related to the 1995 hangings of Ken Saro-Wiwa and eight other protesters by Nigeria's then-military government.

In the case - Kiobel et al v. Royal Dutch Petroleum Co et al, 2nd U.S. Circuit Court of Appeals, Nos. 06-4800 and 06-4876, the plaintiffs had sought their claims from the oil giant under a 1789 U.S. law known as the Alien Tort Statute.

The Alien Tort Claims Act (ATCA) was adopted in 1789 as part of the original Judiciary Act. It gave the federal courts jurisdiction to hear tort claims brought by foreigners who allege a violation of international law or a treaty to which the United States is a party. For almost two centuries, the statute was relatively dormant, supporting jurisdiction in only a handful of cases. However, it was later invoked in several cases involving torture, disappearances, or killings committed by non-Americans in foreign countries.

In a divided vote that prompted a bitter debate among some of its judges, the US appellate court affirmed a September ruling, which held that companies cannot be liable in U.S. courts for violations of international human rights law.

Reuters reported that the full 2nd U.S. Circuit Court of Appeals in New York declined to hear the case by a 5-5 vote and instead left intact the original 2-1 panel ruling from September. Separately, the judges in that panel voted 2-1 not to rehear the case, the report said, added that the Friday ruling may not be the end of the lawsuit.

"The 2nd Circuit is alone among federal circuit courts in concluding that corporations cannot be responsible under U.S. law for human rights violations, " the newswire quoted an international law professor at George Washington University, Ralph Steinhardt as saying. "This clears the way for the plaintiffs to seek review at the Supreme Court," he added. The report added that a lawyer who has represented the families, Paul Hoffman, and Shell, did not immediately return requests for comment.

Shell had since denied allegations it is involved in human rights abuses.The 2nd Circuit ruling, the report said, applies in New York, Connecticut and Vermont. The Alien Tort Statute had underpinned other human rights cases. Reuters reported that in one, mining company Rio Tinto Plc was accused of forcing workers in Papua New Guinea to live in "slave like" conditions, and pushing the government to exact retribution after a mine was sabotaged.

The report cited another case where plaintiffs sought to hold Ford Motor Co. General Motors Co. and International Business Machines Corp liable for helping South African authorities when apartheid was in force more than two decades ago.

Friday's split ruling showed major differences in the judges' thinking. Chief Judge Dennis Jacobs, part of the September panel that ruled for Shell, wrote that the original ruling "has no great practical effect except for the considerable benefit of avoiding abuse of the courts to extort settlements."

He chided what he called fears by dissenting Judge Pierre Leval that "slavers and pirates will now rush into corporate transactions," resulting in "absolution to moral monsters. For the record: even moral monsters are humans, and I would happily see them hanged." Leval countered that Jacobs' opinion evinces an "intense, multi-faceted policy agenda" underlying an effort "to exempt corporations from the law of nations."

The report noted that other judges who favored a rehearing by the entire court said the case presented "a significant issue," and that September's ruling conflicted with a 2008 ruling from the 11th Circuit appeals court, which sits in Atlanta.