The Supreme Court upheld the individual health insurance requirement in President Obama's health-care law, a victory for Democrats and Obama. (Read More: What Is the Health Insurance Mandate?) Obama is scheduled to deliver a statement at 12:15 pm ET. (CNBC.com will be streaming this event live.)
The Dow Jones Industrial Average fell sharply, led by JPMorgan [JPM 35.4001 -1.3799 (-3.75%) ] and Intel [INTC 25.5599 -0.6601 (-2.52%) ], after finishing higher for the second day in the previous session.
All 10 S&P sectors were trading in negative territory, led by financials and techs.