At the center of Washington v. United States are culverts, the pipes that carry streams under roads. The state has more than 800 culverts blocking more than 1,000 miles of streams. Twenty-one tribes sued the state 17 years ago to fix these culverts, which make salmon migration more difficult.
Professor Robert Anderson, who specializes in Native American law at the University of Washington Law School, said the lawsuit is based on a series of treaties that opened up the state to settlement.
"In exchange for surrendering their claims to most of their land in Western Washington," he said, "the tribes retained an explicit right to fish at usual and accustomed stations in their aboriginal territories."
The state has said it will cost $2 billion to fix the culverts, although Anderson countered there's no evidence for that number and it most likely represents the worst-case scenario.
Washington Attorney General Bob Ferguson acknowledged that the state needs to do more to protect salmon, but said this case could force a costly solution that might not work.
Anderson said the state argued in a lower court that treaties don't offer protections for fish habitat, meaning tribe members have a right to fish, but the state doesn't have to guarantee there are any fish to catch. Washington has backed away from that argument in the Supreme Court case.
The verdict could have implications for other tribes, and for the habitat protections in treaties, although Anderson says these salmon-blocking culverts set a high bar.
"One thing I can say about this case," he said, "is that the harm is so clear that's being caused by these culverts that it's difficult to see how another case could match this level of hardship that the culverts are causing."
Still, he said, tribes in the West and Midwest are watching the case closely, because of its potential effects on their treaty rights to fish and hunt.
The case is online at supremecourt.gov.