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James E. Dennehy, the highly respected leader of the largest and most important field office in the bureau, said in an email to staff that the F.B.I. was in “a battle of our own.”

Carter was president from 1977 to 1981, but he was perhaps more famous for the life he led after he left office. He was one of the biggest advocates for peace, democracy and human rights.

Federal agencies have opened at least three reviews into whether the company and its leader complied with disclosure protocols intended to protect state secrets, people with knowledge of the matter sa...