Here's the case that the U.S. Federal Government's Solicitor General (their trial lawyer) made yesterday May 10, 2011 in Federal Appeals Court, in defense of Obamacare:
The Solicitor General for the United States, Neal Kumar Katyal, today claimed in a federal appeals court hearing that
Congress has the absolute power to order citizens to purchase consumer goods if lawmakers believe there is a national problem the purchases would address.
"Could they [the Federal Government] possibly require the purchase of wheat?" he said. "The answer is yes."