Nairobi police were waiting at the airport with a search warrant last week when Kenya's 28-year-old Tom Mboya got off the plane after a trip to the U.S. to receive an honorary degree at Howard University in Washington, D.C. For 2½ hours, as Mboya stood calmly aside, officials examined everything in his luggage. Reason for the bureaucrats' interest: on the flight home, Kenya's most dynamic African leader had stopped off at Tunis to meet with other leaders of the All-African People's Conference, formed last year in Ghana, which brought together for the first time African leaders from every...