They could declare users inadmissible - perhaps for life. He also noted that sniffing dogs can smell residue weeks after it's been used so people crossing should not lie if the questions are asked.
Canada is set to become the world's only major industrialized nation to legalize retail marijuana sales, starting October 17. Owen said if travelers lie about past drug use during questioning, that's "fraud and misrepresentation, which carries a lifetime ban".
Not every traveller will be asked whether they use marijuana, but Owen also outlined several signs of pot use that officials will not ignore.
LeBron James reacts to Canelo Alvarez-Gennady Golovkin fight
After 12 rounds, Alvarez would be announced the victor of the bout via majority decision, winning the WBC middleweight title. With scores of 114-114, 115-113 and 115-113 the other way, Golovkin saw his WBA and WBC middleweight belts handed to Canelo.
Meanwhile, during an interview with CBC Manitoba earlier this week, Prime Minister Justin Trudeau said the federal government is working with us officials to ensure that travel to the States doesn't become an issue when marijuana is legalized in Canada next month.
He will then be giving the opportunity to "voluntary withdraw" from the border-or face "expedited removal".
Owen gave Politico a detailed preview of how the US Customs and Border Protection agency will continue to apply long-standing US federal laws that treat marijuana as a banned substance and participants in the cannabis industry as drug traffickers. The waivers are only granted at the discretion of CBP.
"I think it's incredibly risky for someone to [lie], especially if they are somebody who works in the industry and their affiliation with the industry is readily available online", said Enenajor.
This Is Why The US Are Really Panicking About Hurricane Florence
A woman walks her bike across a street near a boarded up bar a day before the arrival of Hurricane Florence in Wilmington . The first tropical storm-force winds of at least 39 miles per hour (63 kph) were forecast to hit the coast on Thursday.
Anyone who travels to the USA regularly knows that a common question at the border is "what do you do for a living?"
"We don't recognize that as a legal business", Mr. Owen added. "Facilitating the proliferation of the legal marijuana industry in USA states where it is deemed legal or Canada may affect an individual's admissibility to the U.S.".
"I wouldn't presume to have any other country tell me how or who we can let into Canada, and I certainly won't work to assume to impress upon the USA who they have to let in or not".
"A lot of people don't understand that they are still going to have problems after legalization", said Henry Chang, a partner at Blaney McMurtry LLP in Toronto who handles immigration law on both sides of the border. Justin Trudeau's government and travel agents are warning Canadians to make sure they have no trace of the drug in their cars or luggage.
Man dies from injuries suffered in shark attack off Cape Cod
Lytton was airlifted to Tufts Medical Center in Boston, where he was treated for deep puncture wounds to his torso and leg. However, shark sightings around the Cape have reportedly been more frequent this year, leading to several beach closings.