Tim Jost, a Washington and Lee University law professor and a prominent supporter of the healthcare law, said the mandate’s critics invited the new line of defense by urging the court to strike down the entire law. The states say the mandate cannot be “severed” from any of the law’s other provisions. That position basically concedes that the mandate is necessary to make other reforms work, Jost said.

“I think that is their strongest argument,” Jost said of the Necessary and Proper Clause.

Justice is by no means abandoning its argument that the mandate is Constitutional under the Commerce Clause.

Both critics and supporters of the law think the administration could be trying to appeal to Scalia with the shift, as the line between the Commerce Clause and the Necessary and Proper Clause was central to an important decision of Scalia’s.