Canada has became the first major world economy to legalise recreational cannabis, kick-starting a nationwide experiment in drug laws and regulations despite uncertainty about the consequences.
Weed enthusiasts celebrated the "end of prohibition” as the clock struck midnight on Tuesday evening and the first legal pot sales for non-medical purposes were made across the country.
Justin Trudeau, the Canadian prime minister who pledged the change in his 2015 election campaign, tweeted that the policy would take “profits out of the hands of criminals” and protect children.
On Wednesday, his government also announced moves to make it easier for people convicted for carrying small amounts of marijuana in the past to obtain a pardon, waiving the $631 Canadian dollar fee.
However legalisation was not universally welcomed, with one leading Canadian medical journal warning the “uncontrolled experiment” would put profits ahead of the nation’s health.
And there was speculation about the impact the change could have on other nations, including America – where some states have legalised recreational use – and even Britain, where it remains a crime.
Canada is the first country in the G7 – a group of the world’s seven biggest economies – to legalise recreational cannabis, overturning a ban almost a century old. It has had legal medical marijuana since 2001.
The change is the latest example in a growing trend of countries loosening their cannabis laws.
Uruguay became the first country to legalize the sale of cannabis for recreational use in 2013. Portugal and the Netherlands have decriminalised the drug.
South Africa’s top court has said cannabis use at home is legal. And in America, nine states have legalised recreational use and more than 30 have approved medical marijuana.
In Canada, adults can now buy cannabis oil, plants and dried cannabis from licensed producer and retailers. They can also carry 30 grams (one ounce) of the drug in public.
At least 111 legal pot stores opened across the nation on Wednesday, starting first in Newfoundland, Canada’s most easterly province where the time turned midnight before the rest of the country.
Excited smokers waited outside stores to be among the first to buy legal recreational pot, celebrating the historic moment.
Ian Power, who queued in St. John's, Newfoundland, told the Associated Press: "I am going to frame it and hang it on my wall. I'm not even going to smoke it. I'm just going to save it forever.”
Bruce Linton, the CEO of marijuana producer and retailer Canopy Growth who served Mr Power, said some people were in tears.
“The last time Canada was this far ahead in anything, Alexander Graham Bell made a phone call,” he said, referring to the telephone inventor who lived in the country.
The law change has created a patchwork of different regulations across Canada because provinces have been allowed to create their own rules over the specifics of sale.
Some are only allowing government-run stores to sell the drug, others have agreed to give licenses to private retailers. Some provinces have gone for a mix of both.
One concern to have arisen is whether the police are prepared for a possible spike in drug driving. There are doubts about the reliability of screening technology and fears cases could clog up the courts.
Another is at the US-Canadian border. The US Customs and Border Protection held a briefing with journalists on Tuesday, noting that marijuana remains illegal under US federal law and those caught at the border with pot are subject to arrest and prosecution.
Mr Trudeau has defended the change by arguing it will better protect children from cannabis by placing sale in a legal framework, while taking profits away from criminals.
It could also generate hundreds of millions of extra tax revenues a year for the Canadian government.
However on Monday, the Canadian Medical Association Journal issued a scathing editorial saying the country was about to begin “a national, uncontrolled experiment in which the profits of cannabis producers and tax revenues are squarely pitched against the health of Canadian”.
The piece concluded: “If use of cannabis increases, the federal government should have the courage to admit the legislation is flawed and amend the act. Canadians - and the world - will be watching.”
In Britain, the first steps have been taken to loosen the rules around medical cannabis use, with Sajid Javid, the Home Secretary, announcing a review earlier this year.
However Mr Javid said it was “in no way a first step to the legalisation of cannabis for recreational use”.
Bookies issued odds suggesting non-medical use will still be illegal in Britain in 2025.