Despite facing some hesitancy among green groups in her home state, the vice president has embraced the cause since her time as San Francisco district attorney.
The regulation is a major win for advocates from communities with contaminated drinking water who have sought an enforceable limit on the chemicals for years.
The hard-fought negotiations over how to share the pain from shrinking water supplies will affect tens of millions of people and powerful farming interests.
Billions of dollars of Inflation Reduction Act money meant to tackle drought looks likely to make it more expensive to clinch a broader deal critical to economies in several states.
The Biden administration this year finalized a rule to cement broad protections for wetlands. That regulation must now be reworked in light of the Supreme Court ruling.
California, Arizona and Nevada are among the states at odds over how to divide the river’s water — a fight among powerful political and economic interests with dire consequences.
Advocates say the long-running problems at Jackson’s troubled water plant show the largely Black city has been neglected by the Republican-controlled state government.