HALIFAX -- Jean Chretien says politicians have to adjust to changing times, as his own views on marijuana, capital punishment and other contentious issues evolved after he was first elected in the early 1960s.

Whether it's pot smoking, abortion, gay marriage or the death penalty, the former prime minister says he's tried to reflect the spirit of the times -- even if his changing politics put him in conflict with his conservative upbringing in a large, Roman Catholic family in rural Quebec.

"What were certain values 50 years ago, are not the same today. We have to live with that. It's not always easy," he said.

When asked Monday about Prime Minister Justin Trudeau's decision to legalize the sale of marijuana, Chretien said he is in favour of decriminalization.

"What is completely unacceptable, in my judgment, is a young man smoking marijuana will have a criminal record for the rest of his life, (and) he can't cross the border -- come on," Chretien said after a ceremony marking the official opening of a public policy think-tank at Dalhousie University in Halifax.

"It is the modern thing to do ... You have to adjust to the new life."

Chretien did not directly address the issue of legalization, nor did he indicate whether he was at odds with the approach taken by the federal government.

When Chretien was prime minister, his government tried in 2003 to pass a law decriminalizing simple possession of small amounts of marijuana, but the bill died when Parliament was prorogued.

Earlier this year, Liberal MP Bill Blair, a former Toronto police chief, said Criminal Code provisions on marijuana must be upheld until legalization is in place.

Blair, parliamentary secretary to the justice minister, is the Trudeau government's point man on the issue.

NDP Leader Tom Mulcair has said the government should decriminalize marijuana right away.

"I'm glad Mr. Chretien agrees with us, that would be my comment," NDP justice critic Murray Rankin said Monday.

Chretien, 82, said he has never smoked cigarettes and he's never tried pot.

"I don't know what it is and I never tasted that," he said. "I don't know what is the effect."

First elected to the House of Commons in 1963, Chretien said his constituents in Shawinagan, Que., gave him a hard time when he voted against capital punishment.

"People thought I was wrong," he said, adding that he faced more opposition from locals after a landmark Supreme Court of Canada ruling that decriminalized abortion in 1988.

"I'm a Roman Catholic from a large family. To vote in favour of letting ladies decide what to do with their own bodies -- it was not easy for me ... (But) I did that."

And in 2003, Chretien's majority government announced that it would not appeal court rulings supporting same-sex marriage, setting the stage for legislation that would later recognize the validity of such unions.

"We have to adjust to reality," Chretien said. "Marijuana is in the same category."

Chretien was in Halifax to officially open the MacEachen Institute for Public Policy and Governance, a non-partisan think-tank named in honour of former Liberal cabinet minister and Cape Bretoner Allan MacEachen, who is now in his 90s.

Chretien recalled that he worked in the federal cabinet with MacEachen for more than 10 years.

"He was a great parliamentarian ... and a very influential member of the cabinet," Chretien said after he and former Liberal leader Bob Rae reminisced about MacEachen's career at a ceremony that attracted about 500 people.

The son of a coal miner who was first elected to the House of Commons in 1953, MacEachen helped design many of Canada's key programs, including the national labour code, minimum wage legislation, old age pensions and medicare.

"But for us, he was Mr. Cape Breton," Chretien told the crowd, adding that he visited the francophone communities in MacEachen's riding many times, citing Isle Madame, Gros Nez Island and Arichat.

"He was bilingual," Chretien said of MacEachen. "He could speak English and Gaelic."

-- With files from Bruce Cheadle in Ottawa