Shares of online retailers took a hit after U.S. Supreme Court allowed states to force these companies to collect sales tax.

The ruling opens the door to a new revenue stream to fill state coffers - up to $13 billion annually, according to a federal report - while imperiling a competitive advantage that e-commerce companies had over brick-and-mortar rivals that already must collect sales tax.

Near midday trading, just after the ruling was announced:

• Amazon (AMZN) was down 1 percent
• Wayfair (W) was off 3.6 percent
• Overstock.com (OSTK) was down 2 percent
• Etsy (ETSY) fell 4.3 percent
• eBay (EBAY) slid 2 percent
• Shopify (SHOP) tumbled 3.4 percent.

Amazon already collects state and local sales taxes. Amazon was among the biggest drags on the benchmark S&P 500 stock index.

The justices, in a 5-4 ruling against Wayfair, Overstock and Newegg Inc., overturned a 1992 Supreme Court precedent that had barred states from requiring businesses with no “physical presence” in that state, like out-of-state online retailers, to collect sales taxes