“When injustice is/becomes law, resistance is/becomes duty” has been credited to such famous figures as Thomas Jefferson (1743-1826) and Nelson Mandela, but there’s no evidence that either person ever said it. One Wiki Answer has stated that the expression comes from the Civil War, when the Confederate States of America had allegedly used “When tyranny becomes law, rebellion becomes duty.” However, the “tyranny?rebellion” version became popular from about 2008; Google Books doesn’t show a single match for that phrase.
 
“When injustice becomes law, opposition is a duty” was used in West Germany in 1979 and “When injustice becomes law, nonviolent resistance becomes duty!” was spoken by Petra Kelly (1947-1992)—who co-founded the German Green Party in 1979—at a rally in Nuremberg in 1983.
 
The saying appears to have been popularized in Australia. A 1983 pamphlet, published in Sydney by Women’s Action Against Global Violence, was titled Pine Gap, the images: When injustice becomes law, resistance becomes duty. The Green Left has used “When injustice becomes law resistance becomes duty” since at least 1992. 
 
“When injustice is/becomes law, resistance/rebellion is/becomes duty” has been printed on many gift items, such as T-shirts, bumper stickers and posters.
 
         
Google Books
Atlas World Press Review
Volume 26
1979
Pg. 39:
The group told Hanover’s Minister-President Albrecht, among other things, “When injustice becomes law, opposition is a duty.” Most of the demonstrators wore yellow rain jackets bearing the slogan, no to atomic energy.
 
OCLC WorldCat record
Pine Gap, the images : when injustice becomes law, resistance becomes duty.
Author: Women’s Action Against Global Violence (Australia)
Publisher: Sydney : Women’s Action Against Global Violence (Women for Survival), [1983]
Edition/Format:   Book : English
   
Green Left (Australia)
Young activists prepare for conference
Wednesday, June 24, 1992 - 10:00
By Sean Malloy
“Resistance takes an active stand on issues important to young people. This year’s Resistance conference will reflect the diversity and dynamism of our activities this year and our plans for the future”, says Jorge Jorquera, assistant national coordinator of Resistance, which is preparing for its 21st national conference.
 
“When injustice becomes law resistance becomes duty”, is the theme of the conference, which will run July 4-6 in Melbourne. Jorquera says the theme reflects the political situation young people face now.
 
Green Left (Australia)
When injustice becomes law
Wednesday, November 17, 1993 - 11:00
Ruth Ratcliffe
“The High Court of Australia’s decision to keep refugee children imprisoned in detention centres makes it crystal clear that injustice has become law in this country”, Lisa Macdonald from the Socialist Alliance said on October 6. “And when injustice becomes law, resistance becomes duty.”
   
Google Groups: misc.activism.progressive
Rich Winkel
6/4/97
(...)
Gareth W R Smith   Activist, Psychologist, High School Teacher
.(JavaScript must be enabled to view this email address)  Voice:06-247-7429 Fax: 06-247-7429
8 Scrivener Street, O’Connor, Canberra City, ACT 2602, Australia
Canberra Program for Peace,  Campaign for an Independent East Timor
“When injustice is law resistance is duty.”
 
Google Groups: misc.activism.progressive
OZ: TIMOR: WHEN INJUSTICE IS LAW, RESISTANCE IS DUTY
Rich Winkel
3/25/98
 
Green Left (Australia)
Protests mark refugee convention anniversary
Wednesday, August 8, 2001 - 10:00
BY KERRY RIDGEWAY
SYDNEY — In the week that marked the 50th anniversary of the UN refugee convention, human rights activists in Sydney and Melbourne mobilised to oppose the government’s policy of forcible detention for all onshore asylum seekers.
(...)
“The Howard government may as well have put the noose around [the suiciding detainee’s] neck”, Free the Refugees Campaign’s Paul Benedek told the rally.
(...)
“We’re willing to provide a safe haven for refugees despite the law”, Benedek continued. “Why? Because when injustice is law, resistance is duty. The law of mandatory detention is arbitrary and inhumane. The law is wrong.”
     
Democratic Underground
Moonbeam_Starlight
Sun Nov-21-04 04:05 PM
When injustice becomes law, resistance becomes duty.
Best. Shirt. Ever.
I just bought a shirt with those words on it. It has a big raised red fist on it.
It’s my new sig. Whatdaya think? Agree?
(...)
Soopercali
Sun Nov-21-04 04:11 PM
3. It’s from Nelson Mandela…
In case you didn’t know.

Tribe.net
Nelson Mandela Tue, September 18, 2007 - 12:32 AM
(...)
COMMENTS
Tue, September 18, 2007 - 8:17 PM
A True Hero
Nelson Mandela is one of my heros too. I am just finishing his bok “The Long Walk to Freedom”. he has a wonderful , rich life’s history.
My favorite quote by Mandela is: “When injustice becomes law…resistance is duty”
Awesome!~ This is a true piece of literary wisdom. Thank you so much.
 
Google Books
Joschka Fischer and the Making of the Berlin Republic:
An Alternative History of Postwar Germany
By Paul Hockeno
New York, NY: Oxford University Press
2008
Pg. 163:
At a 1983 rally in Nuremberg, for example, she (Petra Kelly—ed.) told the crowd:
(...) (Pg. 164—ed.)
“When injustice becomes law, nonviolent resistance becomes duty!”
   
Spogg
2:33 pm, Oct 16 2008
AFstickman M26 wrote:
Lmao… that’s classic.
Anyway, to transform this into a favorite quotes thread:
“When injustice is law, resistance is duty.” -Unknown
 
13 April 2010, The Post-Standard (Syracuse, NY), “Government ‘Taxing’; Tea party rally draws crowd unhappy with the state of the union” by Charles McChesney, pg. A3, col. 2:
Waving American flags, “Don’t Tread on Me” flags and homemade signs that declared everything from “When injustice becomes law resistance becomes duty,” to “End NAFTA” and “Taxed Enough Already,” many in the crowd stood for three hours clapping and cheering as the rolling rally for the tea party movement delivered songs, jokes, speeches and tributes.
 
Google Books
Portrait of a Despot:
The Modern Traits
By Charles Ochen Okwir
Central Milton Keynes: AuthorHouse UK Ltd.
2011
Pg. 179:
In fact, it reminds me of the ancient revolutionary maxim which states that “When Injustice Becomes Law, Resistance Becomes a Duty”.
 
World Socialist Web Site
Greece to miss deficit target and impose more cuts on workers
By Christoph Dreier
3 October 2011
(...)
From the ministry’s balcony hung a banner with the inscription: “When injustice becomes law, opposition becomes a duty”.
 
Serpente Emplumada
TERÇA-FEIRA, 1 DE NOVEMBRO DE 2011
“When injustice is law, resistance is duty” Thomas Jefferson
   
New York (NY) Times
ART IN REVIEW
‘Ruptures’: ‘Forms of Public Address’
By HOLLAND COTTER
Published: September 13, 2012
(...)
The Egyptian muralist who calls himself Ganzeer covered Cairo with the words “When Injustice Becomes Law, Rebellion Becomes Duty” during the Arab Spring last year and ended up in jail.
   
Digital Journal
Calling the White House to save dogs from cops
By Ernest Dempsey
Sep 20, 2012
(...)
Eddie: Let me put it this way. When we see injustice, then we are responsible as American Citizens. Let me quote what Thomas Jefferson said: “When Injustice Becomes Law, then Resistance Is Duty.” Our forefather of this great nation is telling us to act on what is not right; so now you can consider why every citizen should sign this petition, whether you own a dog or not; but we all know someone that does own a dog.