The treaty is the latest sign of growing American Indian activism tied to tribal rights and the environment, and just the third such cross-border agreement in 150 years, tribal members involved said. The U.S. Fish and Wildlife Service said earlier this year that Yellowstone-area grizzlies had come back from the brink of extinction and it proposed stripping U.S. Endangered Species Act protections from the population of about 700 bears.

The move would open the way for hunting bears that roam outside the park's borders in Wyoming, Montana and Idaho. The treaty, expected to be signed by Piikani Nation and other tribes in the western Canadian province of Alberta on Friday, declares support by more than 50 tribes for protecting grizzlies from random killing and preserving their habitat against development. The planned ceremony comes two days before representatives of other tribes mostly in and around the U.S. Rocky Mountain West are expected to sign the same treaty during a ceremony in Grand Teton National Park in Wyoming.

The Canada-based tribes are signing the measure to show solidarity with tribes based in the United States, as they are all united by cultural and religious ties to grizzlies. Chief Stanley Grier of the Piikani Nation and representatives from such tribes as the Blackfeet Nation in Montana and the Shoshone-Bannock of eastern Idaho, argue grizzlies are too sacred and culturally important to be killed by hunters. "There should be no doubt that delisting and trophy hunting the grizzly bear on ancestral tribal and treaty lands threatens irreparable harm to those sites and to tribal sovereignty and religious freedom," Grier said.

Tribal members also say the U.S. government failed to engage in "meaningful consultation" before decisions were made about delisting grizzlies. Serena Baker, a spokeswoman for the U.S. Fish and Wildlife Service, said the agency had sought since 2014 to reach out to about 50 tribes – through letters, phone calls and emails – about Yellowstone grizzlies. "The service has and is continuing to offer government-to-government consultation with Native American tribes west of the Mississippi," she said on Thursday.