The announcement comes on the same day that U.S. activists have blocked the shipment of pipes for the Trans Mountain expansion project

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The federal government is facing a new legal battle against the Trans Mountain pipeline expansion.

Today, the Tsleil-Waututh First Nation announced that it's seeking leave to appeal to the Supreme Court of Canada in connection with an earlier decision by the Federal Court of Appeal.

On September 4, the appelate court granted leave to six First Nations to challenge the Trudeau cabinet's approval of the $9.3-billion project, which will triple shipments of Alberta diluted bitumen to the Lower Mainland.

The Tsleil-Waututh are arguing that the Federal Court of Appeal made a legal error in the way that it narrowed the scope of its challenge, excluding anyting outside the degree of consultation with Indigenous peoples.

“We are taking this issue to the Supreme Court of Canada not only to stand up for our inherent and constitutionally protected rights, but also to make sure that Canada follows their own laws when making decisions,” Tsleil-Waututh Chief Leah Sisi-ya-ama George-Wilson said in a news release.

Among the grounds that the Federal Court of Appeal won't consider are:

* changing economic circumstances, rendering the pipeline project less economically viable;

* the federal government's failure to comply with the Environmental Assessment Act and Species at Risk Act in connection with southern resident orcas;

* and failing to consider the Tsleil-Waututh Nation's aboriginal title and rights.

Meanwhile, two U.S. environmental organizations—Mosquito Fleet and Portland Rising Tide—say that five climbers have locked themselves to a dock in Vancouver, Washington, to prevent pipe from being shipped to Canada to be included in the Trans Mountain project.

The climbers are being supported by dozens of kayakers and other people in small craft in the water near the Washington state port.

Cedar George-Parker, a member of both the Tsleil-Waututh Nation and Tulalip Tribes, said that the pipeline project is a problem on both sides of the border.

"We need people in the U.S. to stand in solidarity and take action to stop this pipeline," he said in a news release. "The border will not divide us!”