The high court stepped into an enormous environmental battle by agreeing to decide the fate of tougher federal regulations for curtailing smog and soot nationwide.
The justices said they will review a federal appeals court ruling that blocked the Environmental Protection Agency from enforcing clean-air standards it adopted in 1997, among the most contentious regulations ever issued by the Clinton administration.
The highest court's decision is expected sometime in 2001.
The dispute carries "profound implications for the health of the American public," government lawyers told the court.
The standards were successfully challenged by a large coalition of industry groups and three states -- Michigan, Ohio and West Virginia.
A three-judge panel of the U.S. Circuit Court of the Appeals ruled by a 2-1 vote last year that the agency overstepped its authority. The appeals court panel said the EPA had interpreted the 1990 Clean Air Act "so loosely" that it unlawfully usurped Congress' legislative power.
The full appeals court voted 6-5 in October against reviewing the panel's decision.
The revised air standards limited the allowable level of ozone, an essential part of smog, to 0.08 parts per million, instead of the 0.12 parts per million under the old requirement. And states for the first time were required to regulate microscopic particulates, or soot, from power plants, cars and other sources down to 2.5 microns, or 28 times smaller than the width of a human hair.
The Clean Air Act authorizes the EPA to issue air quality standards to protect human health. The law says the agency may set pollution limits that "accurately reflect the latest scientific knowledge useful in indicating the kind anextent of all identifiable effects on public health or welfare which may be expected from the presence of a pollutant."
In another decision, the court rejected government claims that cable smut is reaching young children, reports CBS News Correspondent Barry Bagnato.
The high court, by a 5-4 vote, agreed with Playboy's arguments that the 1996 federal law was too broad and violated constitutional First Amendment free-speech rights.
Justice Anthony Kennedy said for the court majority that the government failed to prove the law was the least restrictive means of addressing a real problem.
``Basic speech principles are at stake in this case,'' Kennedy wrote in the 22-page ruling. ``Here, the government has not met the burden the First Amendment imposes.''
The Supreme Court also let stand a ruling that could force airlines to pay a lot more to some passengers whose luggage was lost or damaged.
The court, without comment, rejected an appeal in which American Airlines sought to limit how much it may have to pay for five suitcases that disappeared, or arrived empty, during a family's 1995 trip from the District of Columbia to the Dominican Republic.
The nation's major air carriers told the justices that a federal appeals court ruling in the American Airlines case ``will senselessly harm the airlines and raise the cost of air travel for their passengers.''
Another Supreme Court decision affects the millions of Americans who drive or ride in cars built before federal regulations required air bags. They cannot, when injured in accidents, sue auto makers for not installing the safety devices, the court ruled Monday.
The justices, by a 5-4 vote, said federal regulation of automobile safety pre-empts, or blocks, lawsuits in which people invoke state product-liability laws and contend air bags could have saved them from harm.
The decision killed the lawsuit of a District of Columbia woman who suffered serious head injuries when she crashed her 1987 Honda.