The Prime Minister's Office received a flood of emails opposing the government's bill to implement new pre-clearance measures at Canadian airports and other departure points following a CBC News story on concerns about the powers the bill grants to U.S. border agents, documents show.

It's been eight months since the U.S. Congress passed its version of a law to implement the latest cross-border agreement with Canada.

The U.S. law authorizes its Customs and Border Protection officials to set up pre-clearance locations at more Canadian locations, allowing Canadian travellers to bypass immigration and customs procedures on arrival at their U.S. destination.

Canada was expected to pass its version of the law around the same time. After all, it was Canada that lobbied hardest for the agreement.

But that hasn't happened.

Canada's ambassador to Washington, David MacNaughton, told the Senate foreign affairs committee he is feeling pressure from U.S. legislators, who keep asking when Canada's legislation will pass.

"Please hurry it up, because I'm a bit embarrassed. I leaned on the Americans so heavily and now they're coming back and saying, 'Where's yours?'" MacNaughton told senators in June.

The bill emerged from the Commons with a thumbs-up, but it has yet to pass the Senate.

One clue to the delays may be found in the prime minister's mailbox.

Avalanche of criticism

CBC News has obtained a trove of public communications, mostly emails, sent over a 10-day period following the a CBC News story on controversial aspects of C-23, particularly the new powers it would grant to U.S. border agents working on Canadian soil.

Letters and emails sent on the issue during February, as well as the government's responses, comprise 1,527 pages, made up mostly of hundreds of messages from the public.

Names are redacted and, in some cases, so are the towns and provinces the letters and emails came from.

Government insiders say the volume of mail received was "unprecedented" and took officials at Public Safety by surprise.

The Liberal government received an outpouring of reaction to its bill to expand border pre-clearance with the United States following a CBC News story about new powers for U.S. customs officers on Canadian soil. (Todd Korol/Reuters)

• What is pre-clearance? Pre-clearance allows Canadian visitors to the U.S. to clear U.S. Customs and Immigration while still in Canada at a Canadian port of departure. Eight Canadian airports offer pre-clearance, two more will do so this year. The Port of Vancouver, Vancouver's train station and some B.C.-Washington ferry routes also offer pre-clearance. Later this year, pre-clearance is expected to be introduced at Montreal's train station for Amtrak's Montreal-New York City route.

The documents show the negative feedback included many missives from people who described themselves as Liberal supporters.

"I have been a dyed-in-the-wool Liberal, but you lose my support if you pass this bill," wrote one person from Burlington, Ont., on Feb. 12.

The same morning, a Coquitlam, B.C., resident warned that after reading about the bill, they now "regretted any financial or political support I've ever given the federal Liberal Party in the past, and have resolved, until I see this one modified to prevent detentions of Canadians or permanent residents, never to support your party again."

"I have voted Liberal all my life but will do evering (sic) to bring this government down if this bill is passed or any version of it," wrote another.

Powers of detention main concern

Most of the letter writers express concern about parts of the bill that grant new powers to U.S. border agents working in Canada. Those include the right to bear arms and, most controversially, the discretionary power to detain Canadians for further questioning if the U.S. agent is unhappy with their answers.

Until now, Canadians passing through U.S. Customs pre-clearance in a Canadian airport have had the right to simply withdraw their request to enter the U.S. if the encounter goes badly, and leave the pre-clearance area.

Section 31 of Canada's legislation takes away that right.

This is another frightening step to one more impingement of our sovereignty. — A British Columbian

"It infringes on our rights as Canadian citizens by allowing a U.S. authority to detain Canadians while on Canadian soil," wrote a British Columbian. "While I am sympathetic to the needs of national security, I find that this is another frightening step to one more impingement of our sovereignty."

"If I try to cross [the border]," wrote another, "and the questioning is heavily weighted on my background, my religion, my personal beliefs about anything, is uncomfortable, or causes me to fear for my own safety, I should be able to unequivocally say, 'You know what? I've changed my mind, I don't think I want to fly to Atlanta today,' pick up my bags, and leave."

Many writers expressed doubts Canadian border agents would be able to exercise similar powers on U.S. soil.

In fact, the U.S. legislation passed last December does extend the same powers to agents of the Canada Border Services Agency in the U.S. But there are no Canadian pre-clearance facilities at U.S. airports, since it is easier for Canada to screen arrivals at the smaller number of Canadian airports.

Legislation to expand pre-clearance has passed the U.S. Congress, but it doesn't affect agents of the Canadian Border Services Agency, who don't work at U.S. airports. (Darren Calabrese/Canadian Press)

Among writers worried about how the changes would affect them, some were concerned by the Trump administration's move to impose a version of the Muslim ban Trump promised during the 2016 campaign.

"Given how U.S. citizens and green card holders were turned out based on their religion last month, I don't believe my fears of being detained and questioned are unfounded," wrote a resident of Hamilton, who described themselves as a dual citizen of Canada and the U.S.

A Calgary writer was concerned about interviewing for a visa in order to take a job offer from a company in Florida. "I am terribly afraid that this bill will hurt my chances of potential employment. … The fact that an American border agent can arrest me on Canadian soil for walking away from an interview, which is what this bill would enable, deeply disturbs me!"

Taking heat from both sides

While many letters referenced the Trump administration's perceived hostility to some ethnic and religious groups and called on the Trudeau government to stand up for refugees and Muslims, the pre-clearance bill also came under fire from people on the other side of the spectrum.

One writer emailed Public Safety Minister Ralph Goodale: "I understand the Americans wanting that right, or authority. This would be due in part to Trudeau's plan to bring in thousands of unscreened, so-called refugees to Canada and park them along the U.S. border."

But the writer agreed with others that while "the Americans have the right to protect their country … they don't have the authority nor should they to detain Canadians on Canadian soil. This authority should not even be considered."