=== Aktivisme ===
Under [[Vietnamkrigen]] tog ham en pause fra arbejdet med retssager for at engagere sig i fredsarbejde. Han har skrevet flere bøger om behovet for en international strafdomstol. Dette arbejde var en væsentlig del af grundlaget for [[Den Internationale Straffedomstol|Den internationale strafdomstol]] og Ferencz var inviteret da domstolen gennemførte sin første sag.<ref name="Welt"/><ref name=":0"/><ref>Ferencz, B. B. (2007). Enabling the International Criminal Court to punish aggression. ''Wash. U. Global Stud. L. Rev.'', 6, 551.</ref> Han holdt afslutningsindlægget for anklagersiden i strafdomstolens første sag (mod [[Thomas Lubanga Dyilo]]). Det var da den anden gang Ferencz havde en sag i retten og han var da 91 år.<ref name=":1">{{Kilde nyheder|url=https://www.washingtonpost.com/lifestyle/style/the-last-surviving-nuremberg-prosecutor-has-one-ultimate-dream/2016/08/31/3b1607e6-6b95-11e6-ba32-5a4bf5aad4fa_story.html|title=The improbable story of the man who won history’s ‘biggest murder trial’ at Nuremberg|last=|first=|date=21. august 2016|work=Washington Post|page=|quote=Ferencz has lived long enough to participate in the first case before the International Criminal Court. At age 91, he gave a closing statement in the prosecution of Congolese warlord Thomas Lubanga Dyilo in Uganda.}}</ref><ref>{{Cite web|url=https://www.cbc.ca/radio/thecurrent/the-current-for-march-21-2017-1.4032985/i-m-boiling-with-anger-97-year-old-nuremberg-prosecutor-won-t-give-up-on-peace-1.4033000|title='I'm boiling with anger': 97-year-old Nuremberg prosecutor won't give up on peace {{!}} CBC Radio|access-date=2018-12-12|first=CBC Radio ·|last=March 21|language=en}}</ref> Han holdt åbningstalen da oprettelsen af domstolen blev drøftet på en stor konference i Rom i 1998.<ref name="Stuart">Stuart, H. V., & Simons, M. (2009). ''The Prosecutor and the Judge: Benjamin Ferencz and Antonio Cassese, Interviews and Writings.'' Amsterdam University Press.</ref><ref>{{Kilde bog|titel=Hvem sa at fred er umulig?|isbn=8247601516|sted=Oslo|udgiver=Genesis|url=http://urn.nb.no/URN:NBN:no-nb_digibok_2009042004074|side=}}</ref><ref>Ferencz, B. B. (1998). International Criminal Courts: The Legacy of Nuremberg. ''Pace International Law review'', 10, 203.</ref> Han argumenterede for at USA skulle slutte sig til den internationale strafdomstol, blandt andet i form af et indlæg i ''New York Times'' sammen med Robert S. McNamara (McNamara var forsvarsminister under optrappingen af USAs deltagelse i [[Vietnamkrigen]] og ville selv have risikeret tiltale).<ref>{{Kilde nyheder|url=https://www.nytimes.com/2000/12/12/opinion/for-clinton-s-last-act.html|title=Opinion {{!}} For Clinton's Last Act|last=McNamara|first=Robert S.|date=2000-12-12|work=The New York Times|last2=Ferencz|first2=Benjamin B.|page=|language=en-US|issn=0362-4331|quote=With the stroke of a pen, President Bill Clinton has a last chance to safeguard humankind from genocide, crimes against humanity and the ravages of war itself. He must simply sign a treaty, finalized in Rome in 1998, to create a permanent International Criminal Court.}}</ref><ref>{{Kilde nyheder|url=https://www.nytimes.com/2019/02/21/movies/prosecuting-evil-review.html|title=‘Prosecuting Evil’ Review: At 98, His Passion for Justice Hasn’t Dimmed|last=Kenigsberg|first=Ben|date=2019-02-21|work=The New York Times|page=|language=en-US|issn=0362-4331|quote=Robert S. McNamara came to write an odd-couple Opinion article in The New York Times in 2000 urging Bill Clinton to sign the treaty creating that court, even though McNamara could have been one of the first defendants.}}</ref>
Hundredårige Samfund