A politician who towered over the half-century since the Second World War, he quietly celebrated his 76th birthday last month. He was prime minister for 16 years, remains active as counsel to a large Montreal law firm, promotes international trading and investment deals, and has a book on foreign policy coming out this month. But, when it came to the referendum, Mr Trudeau announced he was getting out of town.
Liberals and former colleagues urged him to sit this one out, because his vision is now seen as anathema to many young Quebeckers.
Even so, his past deeds were never far from voters' minds. The Bloc Quebecois leader, Lucien Bouchard, managed to rekindle old resentments about the purported "humiliation" of Quebeckers in 1982. Mr Trudeau, with the support of nine provinces, but against the wishes of the separatist Quebec government of the day, had "patriated" the Canadian constitution from Westminster and introduced a Charter of Rights.
The separatists focused criticism on the past role of the present Prime Minister, Jean Chretien, as Mr Trudeau's minister of justice and one of his principal allies. But it was the former prime minister's notion of the nature of Quebec society that took more of a beating than his constitution last week.
Rather than build walls around the province to protect its language, religion and culture, Mr Trudeau said Quebeckers would prosper most by playing a strong role in the whole of Canada, in Ottawa. He also created a bilingual civil service, and engineered the machinery of the national government to operate in both languages equally.
His successor as prime minister, Brian Mulroney, struck a deal with Quebec, and several other provinces, in the late 1980s to implement a package of constitutional amendments. Known as the Meech Lake Accord, it would have led to the Quebec government's agreement to the 1982 constitution, and Mr Trudeau came out of retirement to oppose it.
Quebeckers did not need the protection of a clause in the constitution recognising the province's distinct society and special protection for its language and culture, he argued, because they were capable of competing with other Canadians on an equal footing. His intervention catalysed opposition to the accord in English-speaking Canada, which eventually prevented ratification. When the Mulroney government made another attempt at constitution-rejigging through a national referendum in 1992, Mr Trudeau gave a speech to a group of his admirers at a Montreal Chinese restaurant called Maison du Egg Roll, and helped defeat the measures.
Mr Trudeau still commands attention whenever he speaks or travels and he continues to cut a dapper figure, often appearing at balls or theatre openings with an actress or dancer on his arm. They are invariably beautiful. He has been divorced from Margaret, the mother of his three sons, since the mid 1970s. But his reputation as a roue was enhanced when, at 72, he fathered a daughter. But Mr Trudeau and his vision have always been more popular outside Quebec than within.
So, faced with the results of last week's referendum, which showed that it was only the English Quebeckers and immigrants who prevented a separatist victory, Mr Chretien accepted the new reality.
He will now attempt to implement a new "distinct society" clause, as well as devolving some federal powers to the provincial governments - all to meet what is perceived as Quebeckers' thirst for change. And everybody is waiting to see if Mr Trudeau once again joins the fray to oppose them.