What makes McCollum's pressure campaign to protect the area unusual is how publicly she has appealed to leaders outside the U.S. for intervention.

The extent of the Canadian government’s willingness to engage is unclear. Communities and First Nations in Ontario upstream from the Twin Metals mine site question whether they’ll get to air their concerns about a massive resource development project that would be just miles away and subject to U.S. permitting rules.

Any construction on the proposed copper mine, which environmentalists say poses the risk of leaching toxic slurry into the Boundary Waters, is likely years away. Proponents argue the mine would bring jobs to an economically distressed area of the state and would yield minerals integral to advanced technologies ranging from smartphones to wind turbines. The canoe wilderness is a federally protected area that doesn’t allow even motorized fishing boats and limits the number of canoe permits to keep the number of people there at any given time low.

Canadian Prime Minister Justin Trudeau. | Leon Neal/Getty Images

Trudeau has just come off a rocky few years with the president during which Canada grappled with the possibility that free trade with its biggest customer would evaporate. It's unclear he’d readily go to bat again over something like the mine, which is owned by a subsidiary of Chilean mining conglomerate Antofagasta.

Deputy Prime Minister Chrystia Freeland said last month that the Liberal government is “very engaged” on the issue, though she offered no specifics. “It’s a proposal for a future project and it’s something that Canada definitely is involved in and will continue to work with our American partners on,” she said.

The Canadian government has signaled its wariness. “Canada is concerned about the potential for increased mining activity within the basin which could contaminate boundary waters if not properly assessed and managed, putting Canadian water quality and ecosystems at risk,” Global Affairs Canada wrote in January 2019 to the U.S. Bureau of Land Management as part of the public comment process for the agency’s draft environmental assessment of renewing the mineral leases.

The Canadian government asked BLM to clarify how federal and state governments will coordinate separate review processes to account for potential cross-border impacts, plus how BLM will interact with Canada “to better understand potential impacts to Canadian waters and ecosystems.”

Becky Rom, national chairwoman of the Campaign to Save the Boundary Waters, said she checks regularly with Canadian officials and believes they've yet to receive a response from BLM. Katherine Cuplinskas, a spokesperson for Freeland, did not comment on whether the government had received answers to its questions.

BLM renewed Twin Metals Minnesota’s leases on May 15, and the company formally applied for federal and state permits in December. The Trump administration has moved to speed up environmental reviews and permitting processes for certain projects, but state regulators are conducting a separate review. The company says it expects those studies to take five to seven years.

The International Joint Commission, a binational agency borne out of the 1909 treaty, is advising both governments on environmental issues tied to mining activity through the International Rainy-Lake of the Woods Watershed Board.

"Together, these represent the most appropriate forums to discuss the potential impacts and mitigation measures related to current mining activities and any new mining projects within the Rainy River Watershed," said Twin Metals spokesperson Kathy Graul.

Still, some community leaders in Ontario are beginning to agitate for Canada to do more to notify communities near the watershed about the project and its potential impacts.

Douglas Judson, a municipal Council member in Fort Frances, Ont., said his community — which borders Minnesota and is in the pathway of water flow from where the mine would be built — is still gathering information about the proposal. He said he suspects engagement has been limited in part because Global Affairs Canada is handling the issue due to its diplomatic implications.

“I think that if the project were in Canada, there would be a very different discussion happening right now, and right now there’s no discussion happening," he told POLITICO.

McCollum, whose district covers the city of St. Paul and is nearly 250 miles from the proposed mine site, is using her role as an appropriator to try to put the brakes on the project. She slipped language into the fiscal 2020 spending bill that required the State Department to report back to lawmakers on the effects of sulfide-ore copper mining in the area and U.S. plans to mitigate the risk of cross-border pollution.

The department sent lawmakers an eight-paragraph response that McCollum called “embarrassingly inadequate.” She called on Ottawa to compel the Trump administration to release the “confidential” report in a scathing Feb. 20 statement.

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McCollum has said she plans to continue to press the issue during the fiscal 2021 appropriations process, specifically promoting “the need for a mining pollution early-warning system to protect our cross-boundary waters and prevent treaty violations.” She also has introduced a bill to effectively yank the leases from Twin Metals Minnesota by permanently withdrawing 234,328 acres of federal land in the Rainy River Watershed from most resource development.

In 2016, the Obama administration proposed banning mining there for 20 years. The Trump administration canceled an environmental study of that proposal in 2018 and has refused to release any preliminary findings. McCollum attempted to revive the study in the fiscal 2020 spending measure for federal resource and environmental agencies, but the White House won out during eleventh-hour negotiations over the broad appropriations package.

The project isn't without support in Congress. GOP Rep. Pete Stauber, who represents the district where the mine would be built, has blasted McCollum's attempts to get in the way. His Democratic predecessor, former Rep. Rick Nolan, also supported the mine. Democratic Sens. Amy Klobuchar and Tina Smith haven't opined one way or the other but have called on the administration to finish the environmental study.

Even so, the project isn't without challenges in the U.S. legal system. A federal judge heard oral arguments in a lawsuit challenging the Trump administration's reinstatement of the leases in December.

Judson said he's communicated with the office of rookie Liberal MP Marcus Powlowski, whose riding includes Fort Frances, to bring together bureaucrats from Global Affairs and Environment and Climate Change Canada to discuss the project's implications in his community, which includes a number of First Nations.

“Canada is going through a moment right now on engagement and the role for Indigenous communities in environmental conservation and resource development,” Judson said.

Diplomacy, he said, is “maybe sacrificing that community engagement right now, and that is a little bit troubling.”