In a 6-3 decision, the Court ruled that the law could apply to the plaintiffs, which included organisations seeking to aid the Kurdistan Workers Party (PKK) and the Liberation Tigers of Tamil Eelam (LTTE), even if they were seeking to teach non-violent methods of dispute resolution. Both groups were deemed as terrorist organisations by the American government in 1997.

"The PKK and LTTE are deadly groups," Chief Justice John Roberts wrote for the majority. "It is not difficult to conclude as Congress did that the taint of such violent activities is so great that working in coordination with or at the command of the PKK and LTTE serves to legitimise and further their terrorist means."

President Carter said the ruling threatens the existence of the Carter Center, an organisation he set-up to promote human rights and mediate in international conflicts.

VIEW ALL

"We are disappointed that the Supreme Court has upheld a law that inhibits the work of human rights and conflict resolution groups," Carter said in a statement distributed by the American Civil Liberties Union.

"The 'material support law' - which is aimed at putting an end to terrorism - actually threatens our work and the work of many other peacemaking organisations that must interact directly with groups that have engaged in violence. The vague language of the law leaves us wondering if we will be prosecuted for our work to promote peace and freedom."

However, the decision was welcomed by some legal groups.

"There is no such thing as 'good aid' to a terrorist group," said Richard Samp, the chief counsel of the Washington Legal Foundation.