One of the people responsible for the Safe Third Country Agreement between Canada and the United States says reducing the number of migrants coming into Canada at irregular crossings isn鈥檛 just a question of renegotiating or scrapping the deal, but rather the focus should be on the federal government being able to better control the border.

The irregular border crossing at Roxham Road along the Quebec-New York border has seen a surge in migrants in the last year, and Quebec Premier François Legault has been calling on the federal government to find a solution, while his province struggles to handle the massive increase in people crossing.

Legault鈥檚 plea caused a war of words between Prime Minister Justin Trudeau and Conservative Leader Pierre Poilievre this week, when Poilievre waded into the debate, saying 鈥渋f we are a real country, we have borders. And if this is a real prime minister, he is responsible for those borders.鈥

Trudeau later responded saying that 鈥渋f Pierre Poilievre wants to build a wall at Roxham Road, someone could do that. The problem is we have 6,000 kilometres worth of undefended shared border with the United States, and鈥 people will choose to cross elsewhere.鈥

John Manley 鈥 a former deputy prime minister who served under Jean Chretien and one of the signatories of the Safe Third Country Agreement in 2002 鈥 told CTV鈥檚 Question Period host Vassy Kapelos, in an interview airing Sunday, he doesn鈥檛 think the crux of the problem is whether or not the deal should be modernized or renegotiated.

鈥淚 think there's a separate issue there, which is Canada's ability to control its own borders,鈥 Manley said. 鈥淚 know it's simplistic to say to just block Roxham Road, and the government's right to say, 鈥榳ell we do that and they'll just come in somewhere else鈥. Possibly true.鈥

鈥淏ut fundamental to the nation's sovereignty is the ability to control our borders,鈥 he added.

The STCA was first signed 20 years ago, and there have been talks of modernizing it since 2018, with some changes made in 2019. Under the STCA, people seeking refugee status in either Canada or the U.S. must make their claim in the first country they enter.

The agreement applies only to official land border crossings, which means asylum seekers who manage to enter a country via an unofficial crossing 鈥 such as Roxham Road 鈥 are not returned.

Manley said the nature of the Canada-U.S. border adds challenges: some of the border is over water, much of the border is informal, and in some places, there are even buildings that straddle the line.

鈥淪o it's not without its complexity, but nevertheless, it is something that the government has to be able to do, and to say that if we stop this [irregular crossing], they'll come in somewhere else 鈥 that's not really the point,鈥 he said.

Legault said this week Trudeau needs to discuss renegotiating the Safe Third Country Agreement with U.S. President Joe Biden when he鈥檚 in Ottawa for his first official visit to Canada in March.

But Manley said he鈥檚 unsure how those discussions might go, considering the agreement in its first iteration was something Canada pushed for while the United States was reluctant to sign on.

He said post-9/11, there was 鈥渜uite a large inflow of refugee claimants鈥 from all over the world passing through the U.S. and crossing into Canada to seek asylum. He said they were 鈥渧ery well organized.鈥 The surge in numbers meant Canada couldn鈥檛 keep up, so in the time it took to process their applications, they would settle in Canada, and began to cause 鈥渜uite a strain on social services.鈥

The number of migrants crossing from Canada into the United States was also a fraction of those going in the other direction, so there was little incentive for the Americans to sign the deal in the first place.

鈥淚t is really a question for the Americans,鈥 Manley said. 鈥淚 can tell you that this was a very difficult agreement to achieve.鈥

He added: 鈥淚 think there will be a lot of reluctance on the part of U.S. authorities to give this to Canada without something in return. And I don't know what there might be that we could give in return.鈥

Manley also said the loophole of irregular land border crossings was never a consideration at the time the agreement was signed.

鈥淭he notion that people would come en masse through illegal points of entry seemed unlikely at the time,鈥 he explained. 鈥淚t just wasn't a factor. We didn't really expect it to become one and indeed, it didn't become one for quite a long time.鈥

He said the number of refugees in the world 鈥渂reaks your heart,鈥 and that Canada has a 鈥渞esponsibility as a wealthy country鈥 to welcome them, but 鈥渨e should choose them, and they should come in on a manner in which we provide for their support.鈥

鈥淭he federal government has some responsibility because of its control of the borders to do that,鈥 he added. 鈥淲e shouldn't be leaving cities and provinces stranded because of an uncontrolled flow of people coming in claiming to be refugees.鈥

With files from CTVNews.ca鈥檚 Senior Digital Parliamentary Reporter Rachel Aiello