Mr. Zindani also is a friend and mentor to another Bucailleism devotee of Yemeni descent: Osama bin Laden. The world's most wanted man has regularly sought Mr. Zindani's guidance on whether planned terrorist actions are in accord with Islam, says Yossef Bodansky, biographer of Mr. bin Laden and staff director of a U.S. congressional task force on terrorism. "Zindani is one of the people closest to bin Laden," says Mr. Bodansky, who attributes the book's findings to interviews with various intelligence agencies, current and former terrorists and others.

Mr. Zindani, who stepped down as secretary general of the Commission on Scientific Signs in 1995, is now a leading figure in a Yemeni opposition party that advocates an Islamic state. He isn't listed as a terrorist by the U.S. government. He declined comment for this article, saying through an intermediary that he is preoccupied with political and academic affairs.