In my earlier posts, I talked about using the Supreme Court’s past decisions as a bridge between justices who see the world differently. By tolerating some decisions they disagree with, the justices make the court more than the sum of its parts.

For this to happen, the justices’ commitment to precedent needs to be kept separate from their respective beliefs about how the Constitution ought to be interpreted. It’s perfectly natural for a justice to view decisions as harmful — and in greatest need of overruling — when they reflect approaches to the Constitution that she thinks are misguided. So it shouldn’t shock us if Supreme Court justices who emphasize the Constitution’s original meaning are inclined to overrule decisions that disregard Founding-era understandings. Nor should it shock us if justices who emphasize factors such as contemporary moral values are inclined to overrule decisions they view as out of step with modern times.

As I mentioned yesterday, this doesn’t mean the justices are being unprincipled; it just means they’re applying different principles. But even principled disagreements can create challenges for a system of precedent.

So how should the Supreme Court determine whether to overrule a past decision? In my book, “Settled Versus Right,” I suggest focusing on factors that aren’t tied up with disputes about constitutional interpretation. That paves the way for cooperation among justices who otherwise would find themselves in disagreement. But it doesn’t work like that for every factor that pops up in the course of evaluating a prior case. Believing a decision is flawed isn’t enough to overrule it. It has to be flawed in certain ways. That’s what I’d like to discuss in today’s post.

Let’s begin with an issue the Supreme Court often mentions in its discussions of precedent: whether important facts have changed. To illustrate with an example that has come before the court in recent years, consider the freedom of speech as it applies to broadcast television and radio. Under the court’s prior decisions, broadcasting gets less constitutional protection than other forms of speech. For example, the Federal Communications Commission can fine broadcasters for indecent content even if that content is generally protected by the First Amendment. When it explained this rule in 1978, the court noted that broadcasting was distinctive in its pervasiveness and its accessibility to children. (The court gave some other reasons, too, but I’ll focus on this rationale to illustrate the point.)

Things are different now. It has become harder to argue that broadcasting is worlds apart from, say, cable television or the Internet in terms of its pervasiveness and accessibility. In other words, some key facts have changed. And recognizing that change doesn’t depend on whether a Supreme Court justice thinks the Constitution should be interpreted in light of its original meaning, or contemporary moral values, or whatever else. Everyone can agree that the role of broadcasting in American society has changed quite a bit over the past four decades.

That change presents a good occasion for asking whether the Supreme Court’s approach to broadcasting needs to be updated. Maybe the answer is no. Maybe the distinctive treatment of broadcasting makes sense for other reasons. Or maybe the justices should stay the course to avoid disrupting expectations that have arisen in 40 years under the existing regime. But whether or not the justices ultimately decide to revise the court’s approach, changes in the world of broadcasting justify a fresh look at the issue.

Now imagine a different scenario: The Supreme Court issues a ruling that resolves a constitutional dispute. Several years later, five justices conclude that the decision is wrong. The key facts haven’t changed, but the justices think the decision reflects a misguided way of interpreting the Constitution and has led to problematic results. Is that reason enough to justify an overruling?

Here I think the answer is generally no. A commitment to precedent means more if it overcomes the differences of opinion that keep the justices from viewing the Constitution in the same way. By voting to uphold decisions they disagree with — including decisions that reflect a constitutional philosophy that differs from their own — the justices elevate the Supreme Court above its individual members.

That couldn’t occur, at least not to the same degree, if the justices voted to overrule every decision they viewed as unsound, harmful or otherwise bad. Those determinations depend on underlying theories about the Constitution that vary from justice to justice. They can’t furnish common ground between justices who disagree.

In setting up a system of precedent, it makes sense to require a special justification before overruling a past decision. But the type of justification matters immensely. Some justifications, such as changes in the relevant facts, can be applied the same way by justices with varying approaches to the Constitution. Other justifications, such as the belief that a decision is unsound or harmful, end up dragging disagreements about constitutional theory into the analysis of precedent.

I’ll have more to say about this distinction, as well as its limits, when I’m back tomorrow.