When Marc Emery returns to Canada later Tuesday, after having served his five-year prison sentence in the U.S. for selling marijuana seeds to Americans, the pot activist ​will return to a country where there appears to be "just a lack of enthusiasm on the part of police" to enforce possession laws.

Watch Marc Emery's arrival in Windsor, Ont., live on CBCnews.ca around 4 p.m. ET

"There's a huge amount of discretion. It's kind of the new vagrancy charge, really," said Neil Boyd, professor and director of Simon Fraser University's school of criminology.

A phone survey conducted by Ipsos Reid between Jan. 30 and Feb. 7, 2014, suggested that 70 per cent of 3,000 Canadians polled want to see pot possession either legalized or decriminalized. The margin of error of the poll was plus or minus 1.8 per cent, 19 times out of 20.

But more significantly to the pot law liberalization cause, just a year ago, the Canadian Association of Chiefs of Police proposed a ticketing option for simple possession cases, saying that the current process of sending such cases to criminal court was placing a "significant burden" on the justice system.

"Under the current legislation, the only enforcement option for police when confronted with simple possession of cannabis is either to turn a blind eye or lay charges."

According to Statistics Canada, since 2009, the total number of people charged for marijuana possession hasn't changed that much in recent years — 24,056 (2009), 26,570 (2010), 27,997 (2011), 26,099 (2012), and 25,786 (2013).

'A useful tool' for police

While the number of charges may seem high, it's difficult to determine which ones are stand-alone charges, meaning charges in which individuals were solely charged for pot possession and did not have it tagged on as part of a group of other charges.

"I've heard from some police officers, [the cannabis possession charge] is a useful tool for people who commit other more significant crimes not because it, in and of itself, is particularly problematic," Boyd said. "So it's a lever that can be used against people."

"On the one hand, [police] don't want to chase people for small amounts of marijuana," added Anthony Moustacalis, president of the Criminal Lawyers' Association. "On the other hand, it's sometimes helpful for police to have that in their back pocket if they want to do more intrusive searches of people."

Moustacalis said he believes that the number of marijuana possession charges tends to fluctuate, but that they're generally down.

"They fluctuate depending on the current views of the local police force and any pressure put on them by situations that arise," Moustacalis said.

For example, if police get complaints about people repeatedly smoking pot in a park where parents want to take their kids, police may lay charges to clear out the pot smokers.

'Not being taken as stridently seriously'

In Toronto, however, Moustacalis said there's a policy that the public prosecution service will drop marijuana possession charges if police don't get disclosure, or copy of the evidence, to court in a timely fashion. The result: charges are down, he said.

"It shows that I guess it's not being taken as stridently seriously as it used to be."

In his report, The Enforcement of Marijuana Possession Offences in British Columbia: A Blueprint for Change, Boyd found the RCMP and the Vancouver Police Department have very different approaches and that the RCMP is much tougher in going after marijuana possession offences. Not surprisingly, charges for cannabis possession in Vancouver were much lower than in other parts of the province policed by the RCMP, his report found.

Boyd cited an email from the Vancouver police that noted: "We feel that it is important to note in this debate that the VPD does not place a high investigative or enforcement priority on people for cannabis possession only. In fact, where charges are recommended, in the vast majority of cases the cannabis possession charge is one of usually several more serious offences involved in the same incident."

Moustacalis said the Department of Justice generally has a policy that anyone caught with under 30 grams they will divert the charges, which means the matter will be dealt with in an alternative way that will not result in the person getting a criminal record.

But if someone is charged again or caught with marijuana in a car (where impairment might be an issue) police may be less flexible.

Mostly, Moustacalis said, police will leave people alone if they're smoking marijuana in their own home.

Ten years ago, if there was some pot in the middle of the table, police would charge everybody," he said. "You don't see that. You're basically free to smoke marijuana in your house, unless you're growing a lot of it or there's some issue about you selling it, then they don't bother you."