U.S. Native American tribes and Canadian First Nations are banding together to "collectively challenge and resist" proposals to build more pipelines from tar sands in Alberta, Canada. At least 50 First Nations and tribes signed a treaty on Thursday at ceremonies held in Vancouver and Montreal.

The show of unity comes as a separate protest movement against the four-state Dakota Access Pipeline in the U.S. has galvanized tribes. Earlier this month, as we reported, the U.S. government halted construction in one area particularly sensitive to the Standing Rock Sioux tribe, which led the protests. The Standing Rock Sioux is among the signatories to the treaty.

"We are in a time of unprecedented unity amongst Indigenous people working together for a better future for everyone," Rueben George of the Tsleil-Waututh Sacred Trust Initiative said in a press release.

"Tar sands expansion is a collective threat to our Nations. It requires a collective response," the treaty states. Called the Treaty Alliance Against Tar Sands Expansion, it opposes projects that will expand the production of the Alberta Tar Sands, "including for the transport of such expanded production, whether by pipeline, rail or tanker."

That includes "all five current tar sands pipeline and tanker project proposals (Kinder Morgan, Energy East, Line 3, Northern Gateway and Keystone XL) as well as tar sands rail projects such as the Chaleur Terminals Inc. export project at the Port of Belledune in New Brunswick," according to a statement from the alliance.