For years, Bill McLevin has been travelling to the U.S. on a regular basis to visit his brother-in-law.

Until last week, the 66-year-old Calgarian had never encountered any issues at the border.

McLevin was denied entry at the Sweetgrass border crossing in Montana because of something he did more than 40 years ago — a criminal conviction that was pardoned in Canada.

McLevin was arrested in the 1970s on drug trafficking charges. He served his time in prison, including the 10 years he needed to be pardoned.

"As far as I know, at that time [the conviction] was supposed to be taken off my criminal records," McLevin told the Calgary Eyeopener.

But at the border, McLevin was asked if he'd ever been charged with a criminal offence in Canada. He told the border agent that he had a pardon.

"The next thing he told me was to head into their front office where I had been interrogated and treated like I was a criminal all over again," McLevin said, adding that he was fingerprinted and had his "mug shot" taken.

McLevin said the pardon isn't recognized by the U.S.

"I was being truthful and after I was in the office there ... he told me right away I was denied," he said.

So McLevin and his wife turned around.

Immigration lawyer Michael Greene said he's not surprised by McLevin's story.

"This is an old problem that is going to get worse with a hardening of the border and increased information sharing," he said.

It doesn't matter that McLevin had been pardoned, Greene explained. The U.S. doesn't recognize Canadian criminal pardons and so it comes down to the original conviction. Every country has its own inadmissibility rules, Greene explained, which means some criminal convictions will render a person inadmissible to a certain country without a waiver.

For example, U.S. citizens with an impaired driving conviction are considered inadmissible into Canada, whereas Canadians with that conviction are allowed into the U.S.

In McLevin's case, having a conviction for trafficking does not bode well.

"They're nuts on narcotics," Greene said. "Even though there are many states in the U.S. that have now legalized marijuana, the federal government hasn't changed their position [on drugs]."

Greene said McLevin's only option would be to apply for a waiver, and his pardon may help him in that application.

He recommended that others with previous criminal convictions consult with a U.S. immigration lawyer before attempting to cross the border.

Greene added that the Donald Trump administration has made it clear that there will be a tougher approach to border security.

"You can expect greater scrutiny," he said. "Just because you''ve been able to cross 50 times in the past, don't think that the 51st is going to be clear sailing."

McLevin said he's not sure when he's going to go back to the U.S. He could apply for the entry waiver, but said the cost nears $600 US.

"I'm just so furious over this," McLevin said. "I haven't even watched CNN national TV anymore. I am that much against the Americans."

"I am going to spend my time and my money in Canada."