The Supreme Court will hear arguments on two questions about ObamaCare today. Reason's Nick Gillespie already outlined the basic case against the law's Medicaid expansion here. (Read my take on the states' case against the Medicaid expansion here.) 

The court will also hear arguments on the question of the law's severability. Because the law was passed without a severability clause, which would have ensured that remaining parts of the law would stand should any part be overturned, the court will have to decide how much of the law to strike and how much to let stand should it rule that the mandate (or any other provision) fails to pass constitutional muster. There are three plausible outcomes:

  1. The whole law goes down. This is the position being argued by the 26 states challenging the law. It's also the position that Judge Roger Vinson took when he struck down the entire law in a lower court last year. One thing to note about Vinson's ruling is that although he scrapped the entire thing, he did not actually rule in favor of the states on the Medicaid expansion. He simply said that the mandate was unconstitutional, and that the whole law was woven too tightly to try to remove just one provision. 
  2. The mandate goes down, as do the law's major insurance regulations. This is the position being argued by the administration, which says that the rules banning insurer discrimination against indidivuals with preexisting conditions cannot stand without a mandate. The administration points to market meltdowns in the states to make its point. 
  3. The mandate goes down, but the entire rest of the law stands. This is the position taken by the 11th Circuit Court of Appeals in Atlanta, which heard the case following Judge Vinson; it will be argued by an outside lawyer. 

The administration is correct that the insurance regulations are deeply connected to the mandate. But so is the rest of the law. And that's why the whole thing should go.

In deciding what parts of the law to sever in the absence of a severability clause, the court is in a somewhat dicey position as it has to determine what Congress would have done had the unconstitutional provisions not been available as options. It is of course impossible to know the counterfactual. But it's relatively easy to make a case that the mandate—the provision most likely to be judged unconstitutional—ties the entire law together; after all, the Obama administration has repeatedly argued that the mandate is essential to the law. Nor is it the provision merely essential to the law's functionality; it can also be argued that the provision may have been essential to the law's passage. As Cato's Ilya Shapiro told me back in 2010, "It could be that nothing would’ve passed without the individual mandate—because the bill was a whole bunch of logrolling, finely balanced compromises, etc.—in which case even more falls than just the provisions directly related (including the Medicaid expansion)." If the mandate—or any part of the law—is held to be unconstitutional, then the rest of the law should be thrown out too. 

From the archives: If ObamaCare's mandate is struck down, then what?

Update: Striking down the entire law was always going to be a long shot, even more so than simply striking the mandate. And it looks like several justices on the court are less than interested in taking the entire law down. Via the AP:

Several Supreme Court justices seemed receptive Wednesday to the idea that portions of President Barack Obama's health care law can survive even if the court declares the centerpiece unconstitutional.

On the third and last day of arguments, the justices seemed skeptical of the position taken by Paul Clement, a lawyer for 26 states seeking to have the Patient Protection and Affordable Care Act tossed out in its entirety.

In their questions, Sonia Sotomayor, Elena Kagan and Ruth Bader Ginsburg - and even conservative Chief Justice John Roberts and Justice Antonin Scalia - seemed open to the idea that the wide-ranging law contains provisions that can be saved - even if the mandate for Americans to have health insurance is struck down.

Update 2: The severability argument is now complete. Other reports from observers in the court room suggest it's tougher to predict how the Court might rule. The New Republic's Jon Cohn tweets: "Tough questions to both sides, still hard to predict final verdict, but not out of question SCOTUS throws out entire law." The Examiner's Philip Klein agrees: "Very hard to call where they'll end up," he writes, noting also that "Kennedy argued it may be more extreme to pick & choose parts of law to overturn than to just strike down the whole thing."