[8] In 1967, after Charles de Gaulle said "Vive le Québec libre" while on a state visit to Canada during Expo 67, Allmand sent a message to Paul Martin Sr., the External Affairs Minister, that the rest of the trip must be cancelled.

[9] Allmand was sworn into the Privy Council on November 27, 1972 when he succeeded Jean-Pierre Goyer as Solicitor General for Pierre Trudeau, a post he held until September 13, 1976.

[11][12] In 1976, Allmand signed a warrant requested by Michael Dare, the Director-General of Royal Canadian Mounted Police Security Service, to authorize them to intercept the mail of a Toronto couple.

According to Allmand, the Federal Bureau of Investigation submitted false information to the Canadian government, including an affidavit from a woman with mental disorders who claimed to be Peltier's girlfriend.

[2] After Trudeau's Liberals upgraded their minority government to a majority in the 1974 federal election, they had more leeway to act on abolishing capital punishment.

In 1973, Liberals had renewed the provisions of Bill C-168, passed by Lester B. Pearson's minority government in 1968, which imposed a five-year moratorium on the use of the death penalty.

[15] He also felt that it was illegitimate to grant the Cabinet and the judiciary the power over an individual person's ultimate fate, noting that it is not in line with the values held by Canadian society.

Other opponents accused Allmand and Trudeau of proposing the bill now so that it would not expire before the next federal election in 1979 and risk costing the Liberals votes.

Former Progressive Conservative Prime Minister John Diefenbaker argued that after the Munich massacre, passing Bill C-84 was sending the wrong message in the lead-up to the 1976 Summer Olympics in Montreal.

[14] In response to the calls for referendum, including a motion for a national plebiscite by Alberta MP Gordon Towers, Allmand argued that the role of MPs was to deliberate in the House of Commons, make up their own minds, and then vote.

[14] A year after the vote, Allmand remarked in a speech delivered to Amnesty International, that "Capital punishment, simply because it is immoral and useless, must be fought and defeated if we are to become a world society in which our descendants can live in peace and justice.

He was seemingly about to reach a land claim settlement agreement which would have granted much of the desired political autonomy when he was replaced by Hugh Faulkner in fall 1977.

Faulkner backed away from the concessions that Allmand had made such as control over natural resources, instead proposing a cash settlement and land allotments similar to Indian reserves.

[19] His final cabinet post was as Minister of Consumer and Corporate Affairs from September 16, 1977 until June 3, 1979, when the Liberals were defeated and Progressive Conservative Joe Clark formed government after the 1979 federal election.

[11] In 1995, he gained notoriety for voting against Minister of Finance Paul Martin's budget, as he was opposed to spending cuts that were deeper than promised during the 1993 election and because it did not cancel the Goods and Services Tax.

During the 3rd Summit of the Americas, held in Quebec City in 2001, Allmand encouraged social activists boycotting the event to speak with governmental actors in order to collaboratively develop better policy.

[2] In 2004, Allmand was elected President of the World Federalist Movement–Canada, a position he held until his terminal illness led to his replacement in August 2016 by Walter Dorn.

[31] In November 2005, Allmand was elected to the Montreal city council seat as a member of the Union Montréal party to represent Loyola,[11] in the Côte-des-Neiges–Notre-Dame-de-Grâce borough.

[15][23] In 2011, Allmand supported the Canadian Boat for Gaza, part of the Freedom Flotilla II that sought to deliver supplies to Palestinians.

[36] In 2014, Allmand defended a legal argument, on behalf of the World Federalist Movement – Canada, that challenged the Canadian government's implementation bill for the Convention on Cluster Munitions.

He argued that a clause of the bill which gave Canada an explicit exemption in certain cases while participating in combined military operations with non-signatory allies such as the United States undermined the purpose of the convention.

In August 2021, Somerled Park, near Royal Vale School in Notre-Dame-de-Grâce, part of the constituency that he represented federally and municipally, was chosen to be renamed.