In early 1965 he went to work for the Committee for Non-Violent Action (CNVA) in Voluntown, Connecticut where he participated in and organized demonstrations against the Vietnam War.
Later in 1965 Kellman volunteered with the Student Nonviolent Coordinating Committee (SNCC) in Alabama to help organize independent political parties out of which the call for Black Power came.
Returning North after his work for SNCC, Kellman helped organize the anti-draft movement and the Assembly of Unrepresented People in Washington, DC which was the first mass arrest demonstration against the Vietnam War.
The organizing effort was unsuccessful and Kellman was fired but later won a National Labor Relations Board case against the company.
As president of the local, he was ordered by the company to remove from the union bulletin board a leaflet asking workers to vote to shut down a nuclear power plant in Maine.
However, after the entire shop came out in support of the arrested workers, the company caved and brought the three of them back with pay and told Kellman hereafter they could put whatever they wanted on the union bulletin board.
Kellman's instinct for building solidarity and his organizational skills "turned a routine strike into a crusade marked by rallies, marches, and emotional meetings."
However, the summer prior the start of the strike, Kellman had begun the process of educating and organizing the mill workers into a successful "class-based social movement."
The strikers held out for 16 months until October 1988 when the UPIU’s International President, Wayne Glen, reversed his position and agreed to sign contracts at other IP locations, thus isolating the striking locals.
To help explain the context in which the strike was lost, Kellman wrote a history of the unions in the paper mills called "Divide We Fall," published in 2004.
While working in New Hampshire, Kellman was involved in a bad car accident after which he returned to college and received a BA in Labor Studies from the University of Massachusetts.
While at POCLAD he wrote a number of insightful articles which were published in their journal, "By What Authority", and their book "Defying Corporations, Defining Democracy".
Kellman initiated the "Jay-Livermore Falls Working Class History Project" out of which came the book "Pain on their Faces," a series of essays by participants in the Jay Strike of 1987/88.