By allowing minimum price agreements, the court's 5-4 decision could lead to higher prices, dissenting justices said, as it becomes more difficult for smaller stores and Internet retailers to offer lower-priced goods.

The court said agreements on minimum prices are legal if they promote competition, meaning accusations of antitrust violations will be evaluated case by case.

In a 1911 decision, the Supreme Court had declared that minimum pricing agreements always violate federal antitrust law. But Justice Anthony Kennedy wrote in the majority opinion that the principle that past decisions should be left alone ''does not compel our continued adherence'' in this instance.

Minimum price agreements can benefit consumers, Kennedy wrote, by enabling retailers to invest in greater customer service without fear of being undercut by discount rivals. The agreements also could make it easier for new products to compete, he added, because a retailer could recoup the costs of marketing a new good by charging a higher price.

Dissenting from that view, Justice Stephen Breyer wrote: ''The only safe predictions to make about today's decision are that it will likely raise the price of goods at retail.''

The Consumer Federation of America said in court filings that the ban on minimum price agreements allowed ''innovative retailers to continually enter the market, offering new and lower priced alternatives to consumers.''

Some antitrust experts say consumers shopping on the Internet will be hurt by abandoning the 96-year-old rule.