James Sward readily admits it: he has tried marijuana. More than once. He just never imagined it would get him banned from the United States.

On a recent trip to the U.S., border officials asked the British Columbia elevator mechanic about his drug history. He was honest. Maybe too honest, he said.

He admitted to getting busted carrying pot as a teen – though he was never charged or convicted. But when he admitted to smoking the drug, he was flatly denied entry and banned.

“It’s guys like me that want to tell the truth,” Sward told CTV British Columbia. “The system worked against me, being honest.”

If you have a history of drug-use, telling the truth can indeed get you in trouble at the border, says a U.S. immigration lawyer.

“What I tell people is, you never want to admit, ever, ever using or possessing illegal substances such as marijuana,” Len Saunders said. “(If you get banned) you could require a waiver for the rest of your life.”

Andrew Feldmar found that out the hard way. The Canadian psychologist was famously banned from the U.S. in 2006 after customs officials discovered he used LSD in the 1960s. For a research paper.

“It's totally unfair, totally unjust,” Feldmar said. “If they stopped everybody who has used illicit substances, nobody would be allowed into the United States.”

He’s now able to cross the border with a visa. Sward, on the other hand, is out of luck.

“It’s not worth it, honestly,” he said on fighting the ban.

But if he had to do it all over again, he admits, he just would have lied.

With a report from CTV British Columbia’s Scott Roberts