Its brief made two arguments. One is that the recent Republican tax bill, rather than eliminating the individual mandate, actually made the mandate more onerous by imposing on individuals a legal obligation to purchase health insurance.

The tax bill in fact set to $0 — zero dollars — the penalty for not purchasing insurance. It did not otherwise impose any kind of legal duty on people to buy insurance. Indeed, the president and his congressional supporters repeatedly cheered the law’s repeal of the mandate; they, and the Congressional Budget Office, did not understand the bill to be strengthening it.

The department’s second argument is even more outlandish than its first. It relies on a legal doctrine known as severability, under which courts decide whether the invalidation of one statutory provision requires the court to invalidate related ones. The Justice Department claims that the tax bill’s “super mandate” is unconstitutional (something that no one in Congress or the presidency noticed when they enacted the bill) and that courts must invalidate other rules along with it.

In particular, the Justice Department insists that two popular features of the Affordable Care Act must go, too. The first is the guaranteed issue provision, which prohibits insurers from charging more to people who have cancer, or any pre-existing condition, than to whose who do not. The second is the community rating provision, which prohibits insurers from refusing to sell a policy to someone who can pay the policy’s listed price.

It is hard to overstate just how down-is-up this argument is. Courts determine whether to invalidate other provisions in a law based on their assessment of Congress’s intent and whether Congress would have wanted other provisions to go into effect if one provision did not. The department’s argument is that without the mandate, Congress would not have wanted the guaranteed-issue and community-rating provisions.

But we know the opposite is true: Congress kept the guaranteed-issue and community-rating provisions even after it chose to deprive the mandate of any force or effect in the tax bill.