US Supreme Court ruling curbs power of federal agencies

The conservative-majority US Supreme Court on Friday overturned 40 years of legal precedent to weaken the power of federal agencies, which regulate myriad issues affecting the everyday lives of Americans, from air pollution to food and drugs.

"Courts may not defer to an agency interpretation of the law simply because a statute is ambiguous," said the majority opinion written by Chief Justice John Roberts.

At the heart of the matter is a 1984 ruling in Chevron v Natural Resources Defense Council, which said judges should defer to government agencies in determining a "reasonable" interpretation of the law if the language is ambiguous.

At the time, the case was a win for the administration of Republican president Ronald Reagan, who accused the country's progressive federal judges of burying corporate America under masses of unnecessary and restrictive red tape.

But the political right has since decried the ruling, saying it unfairly empowers the central government over the judiciary and means agencies can alter the meaning of statutes, depending on who is in charge.