US supreme court strikes down Obama's EPA limits on mercury pollution

Justices invalidate new rules in move that could make Environmental Protection Agency more vulnerable to challenges to new regulations on carbon emissions

The US supreme court struck down new rules for America's biggest air polluters on Monday, dealing a blow to the Obama administration's efforts to set limits on the amount of mercury, arsenic and other toxins coal-fired power plants can spew into the air, lakes and rivers.

The 5-4 decision was a major setback to the Environmental Protection Agency (EPA), and could leave the agency more vulnerable to legal challenges to its other new carbon pollution rules, from industries and Republican-led states.