Supreme Court justices, like anyone else, sometimes change their minds.

True, there is stare decisis, the principle that they shouldn’t change their minds too often. Reason: If you expect citizens and the government to obey the law, they need to know what the law is and will be. Also, it’s only fair to treat people in similar situations similarly.

But stare decisis is not a hard-and-fast rule. There have been some famous changes of heart and/or mind, such as Brown v. Board of Education (1954), which reversed Plessy v. Ferguson (1896) and declared racial segregation unconstitutional. Then there’s Lawrence v. Texas (2003), which overturned Bowers v. Hardwick (1986) and invalidated laws against homosexual sodomy. It is generally considered that in both of these cases, the court got it right the second time.

If the court ultimately rules that President Barack Obama’s health-care reform law is unconstitutional, it will be a reversal even bigger than Brown and Lawrence. And there will be no comforting consensus that the court has finally got it right.

Ever since Wickard v. Filburn (1942), with only a couple of minor exceptions, the courts have upheld the use of federal power under the Commerce Clause, which gives the federal government the authority to “regulate commerce.” Even the 1964 Civil Rights Act is considered constitutional as a regulation of commerce.

Up for Grabs

Now, maybe the court has been wrong all this time. Maybe the federal government’s authority under the Commerce Clause is much narrower. Maybe that authority doesn’t extend to requiring individual citizens to have health insurance or pay a fine. But if so, it is not only the future of Obamacare that will suddenly be shaky. Every piece of legislation for about the last 70 years that rested on the Commerce Clause will suddenly be up for grabs. This includes the Civil Rights Act. It includes laws protecting the environment and consumers.

Basically anything the government does that has ever been justified by the Commerce Clause will be open to challenge. For the sake of their own sanity and summer recesses, the justices ought to proceed cautiously.

Conservatives also ought to pause and consider all the lectures they have delivered over the past half-century about the need for judicial restraint. Whether authorized under the Commerce Clause or not, all of these laws -- including Obamacare -- were enacted by the democratically elected institutions of government. For the Supreme Court to call them all into question would be a power grab far beyond anything the court has attempted during the long era of conservative griping on this point.

Whenever liberals argue stare decisis, conservatives understandably get suspicious. In theory, it’s a pretty conservative doctrine. It says, things as they are should stay as they are. In practice, conservatives complain, it works like a ratchet: Liberals, when they’re in control, invent new rights, and then conservatives, under stare decisis, are supposed to do nothing about them when their turn comes. But the fact that courts have been upholding legislation under the Commerce Clause for seven decades with virtually no debate does make it seem unlikely that the whole thing has been a giant constitutional misunderstanding.

In 1993, the first year of the Clinton administration, Hillary Clinton was assigned by her husband, Bill, to design a health-care reform plan. The centerpiece of the plan she came up with was an employer mandate. That is, there was a requirement that employers provide health insurance to their employees or pay a fine.

Ferocious Opposition

The opposition to Hillarycare from Republicans was ferocious, just like their opposition to Obamacare more recently -- and in the Clinton case, the opposition was successful. They threw everything they had at her. They got a judge to rule (later reversed) that her plan was illegal because it had been partly designed in private meetings.

One argument they did not make was that Hillarycare exceeded the government’s powers under the Commerce Clause of the Constitution. (Search the New York Times for all of 1993 and 1994. There is just one buried and dismissive reference to the possibility of a Commerce Clause challenge in an article about half a dozen possible legal strategies for challenging Hillarycare.) Is it possible that requiring people to buy their own insurance is unconstitutional but requiring owners of companies to buy other people’s insurance for them would have been perfectly OK?

During the decades it took for the court to come to its senses about segregation and sexual privacy, there were always lots of people on both sides of the arguments. By contrast, as Dahlia Lithwick points out in Slate, the notion that health-care reform with an individual mandate might be unconstitutional was virtually never heard of until the bill passed and the Vast Right-Wing Conspiracy went to work. Professor Randy Barnett, the intellectual father of the Commerce Clause argument, didn’t really start churning out scholarship on the subject until 2011. During the whole debate over Obamacare, it seems, nobody noticed that it was unconstitutional. Now every conservative politician and pundit finds it not just unconstitutional but obviously so.

It was during the Hillarycare debate that Stuart Butler of the conservative Heritage Foundation first proposed a health-care plan based on the individual mandate. Butler says today: “I’ve altered my views on many things. The individual mandate in health care is one of them.” There’s no stare decisis at the Heritage Foundation, apparently.

(Michael Kinsley is a Bloomberg View columnist. The opinions expressed are his own.)

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To contact the writer of this article: Michael Kinsley at mkinsley@bloomberg.net.

To contact the editor responsible for this article: Michael Newman at mnewman43@bloomberg.net.