Before getting to the heart of the case, the justices first wanted to deal with what seemed to be a side issue: Was the penalty imposed by the individual mandate in Obamacare a tax? If it was, the case would run afoul of a 19th-century law known as the Anti-Injunction Act, which said a tax cannot be challenged in court until someone has actually been forced to pay it. Since the Obamacare mandate wouldn't go into effect until 2014, that would mean there could be no court case until then.
No one had challenged Obamacare on that basis; the challengers wanted the case to go forward now. The White House, having argued strenuously during the Obamacare debate that the penalty wasn't a tax, wanted to go ahead as well. So the court, on its own, tapped a Washington attorney to make the argument that the penalty was a tax and therefore the case should not go ahead.
"The Anti-Injunction Act imposes a 'pay first, litigate later' rule that is central to federal tax assessment and collection," said the lawyer, Robert A. Long, on that first day of oral arguments. "The act applies to essentially every tax penalty in the Internal Revenue Code. There is no reason to think that Congress made a special exception for the penalty imposed by (Obamacare)."
After Long made his case, it fell to the administration's lawyer, Solicitor General Donald Verrilli, to argue that no, the mandate was not a tax, and therefore the case was not subject to the Anti-Injunction Act.
At the same time, everyone knew that the next day, when Verrilli planned to argue that the mandate was justified under the Constitution's Commerce Clause, he had as a backup the argument that it was also justified by Congress' power to levy taxes -- in other words, that it was a tax.
Justice Samuel Alito saw the conflict right away.
"General Verrilli, today you are arguing that the penalty is not a tax," Alito said. "Tomorrow you are going to be back, and you will be arguing that the penalty is a tax. Has the court ever held that something that is a tax for the purposes of the taxing power under the Constitution is not a tax under the Anti-Injunction Act?"
"No," answered Verrilli.
At the time, some observers found the whole thing a little boring; the real action would come the next day, when the court got to the question of whether the Commerce Clause could be stretched to include the individual mandate.