Environmental activists in Milwaukee rallied outside the venue where the Democratic presidential debate was about to take place Thursday, calling on candidates to oppose a Canadian energy company's planned expansion of the cross-border Alberta Clipper oil pipeline that has been allowed to move forward without an environmental review.

“Given Enbridge’s poor record of spills and the risk to our community, our waterways and our global climate, we must demand the rejection of the presidential permit that would approve the Alberta Clipper expansion,” Cassie Steiner, a staff member with the Sierra Club, said in a news release.

Canadian energy company Enbridge was blamed for the worst inland oil spill in U.S. history, when a massive pipeline rupture in 2010 contaminated Michigan’s Kalamazoo River and sickened residents.

“We are calling on our presidential candidates to oppose the Alberta Clipper pipeline expansion and to assure a rejection of the presidential permit if elected,” Steiner said.

Presidential approval is required for such cross-border projects, including Keystone XL — which President Barack Obama vetoed last year, saying it would have exacerbated climate change.

Enbridge’s Alberta Clipper line would carry tar sands oil, among the dirtiest type of crude, through Minnesota and Wisconsin. The company wants to expand the capacity of its Line 67 from 450,000 barrels per day (bpd) to over 800,000 bpd, but the State Department permit was clear in limiting that line’s capacity to 450,000 bpd.

In order to skirt the limit, Enbridge constructed a Bypass Project to divert 800,000 bpd from Line 67 on the Canadian side of the border into an older Enbridge pipeline called Line 3. The oil would then be diverted back to Line 67 once south of the border.

Despite the obvious attempt to circumvent the regulatory process, the U.S. State Department accelerated approval of the pipeline expansion without requiring a new review or opening the project to public comment, according to emails submitted as part of a lawsuit filed by the Sierra Club and other groups against the State Department.

The federal court ruled on the case in December, saying it didn’t have the authority to intervene. It left the decision up to Obama or the next president to reverse the decision.

“Enbridge must be held accountable for the risks these plans present to our safety and our environment,” Steiner said. “We must continue to fight the broader pipeline expansion plans that Enbridge is pursuing.”