Republicans, economists urge Supreme Court to strike entire healthcare law

"Without the individual mandate, the ACA’s reforms, including but not limited to guaranteed issue and community rating, would cause a steep increase in premiums – the opposite of Congress’s express intent," the brief states.

Only one lower court threw out the entire healthcare law, and that part of the decision was reversed on appeal. But the law does not include an explicit severability clause, and even the Obama administration has said some other provisions would have to fall along with the mandate. The Supreme Court had to appoint a third party to make the argument that the mandate is completely severable.

The lawsuit before the Supreme Court was filed by 26 state attorneys general and the National Federation of Independent Business. They will file their initial brief on severability today, and the Justice Department will file its first brief on the merits of whether the mandate is constitutional.