Franck was the Murry and Ida Becker Professor of Law at New York University and advised many nations on legal matters, even helping some to write their constitutions.
David Kennedy, of Brown University, called Franck "the leading American scholar of international law".
"[4] Franck's next major book, East African Unity Through Law, was published by Yale University Press in 1965.
The book discussed African federalism in depth, and was largely informed by Franck's own experiences as a constitutional consultant for Zanzibar.
Franck wrote the first chapter, examining the political implications of such an arrangement and argued that the United States needed to stay engaged with Western Europe.
[7] The same year, Franck edited a second book, Why Federations Fail, which returned to many of the themes examined in East African Unity Through Law.
The book analyzed the importance of "how statesman [sic] rationalize their actions", arguing that the cover stories advanced by politicians to disguise acts of aggression had a profound, long-term effect on the international system.
The book combined a theoretical framework for this process with case studies, showing how their theories had been at work in the previous several decades.
Franck was involved in developing constitutions for several African nations which were emerging from British rule Sierra Leone and Rhodesia, which is now known as Zimbabwe.