I've argued earlier that the Court has been right to treat content-based speech restrictions much more harshly than content-neutral speech restrictions. But this left open the question: Why should the Court be so skeptical even about modest content-based regulations, which don't entirely ban certain ideas but merely restrict them while leaving open ample alternative channels? Such a test is applicable to content-neutral restrictions — why not content-based ones? Here is my answer, adapted from my Speech as Conduct: Generally Applicable Laws, Illegal Courses of Conduct, "Situation-Altering Utterances," and the Uncharted Zones, 90 Cornell L. Rev. 1277 (2005).

The Limits of the "Ample Alternative Channels" Inquiry, Both as to Content-Neutral Restrictions and as to Content-Based Restrictions: I have argued that content-based restrictions are dangerous because they risk broadly suppressing certain viewpoints or facts. But one could respond that, instead of presumptively prohibiting content-based speech restrictions, courts could try to prevent serious burdens on speech the same way they do with content-neutral restrictions: by asking whether the restrictions leave open "ample alternative channels" for expression.

I think, though, that the Court has been right to reject such proposals and to treat content-based restrictions as presumptively unconstitutional without an inquiry into how much the restriction burdens speech or into whether the restriction leaves open ample alternative channels. To begin with, the record of the ample alternative channels inquiry in the content-neutral restriction test hasn't been very good. The Court has at times applied it in a demanding manner, for instance insisting that alternative channels aren't ample if they materially raise the price of speaking, make it harder for speakers to reach the same listeners, or subtly influence the content of the message by changing the medium. But at other times, the Justices have treated this requirement as only a weak constraint. Such a disparity is to be expected given the vagueness of the term "ample."

In fact, the chief practical limit on content-neutral restrictions has not been the "ample alternative channels" inquiry, but the political reality mentioned above: Most realistically enactable restrictions on the noncommunicative aspects of speech do leave open fairly substantial alternative channels for expressing the same ideas. So even if the Court underenforces the ample alternative channels prong, few views or subjects will likely be broadly silenced.

But it's much more likely that a politically feasible restriction on the communicative aspects of speech will substantially block people from expressing a particular viewpoint. This is true even when the restriction is framed as facially content-neutral, or even as speech-neutral — consider, for instance, the Espionage Act in Schenck. Judicial underenforcement of the ample alternative channels prong for content-based restrictions would thus be much more dangerous than underenforcement in the context of content-neutral restraints.

The Limits of the "Ample Alternative Channels" Inquiry as to Content-Based Restrictions: Judicial underenforcement of the ample alternative channels prong would also be more likely when the case involves content-based restrictions, whether they are facially content-based or content-based as applied. "Ample" is a vague term, and one that requires contestable predictions about the law's effects on a complex system of speakers and listeners. There is a large gray area in which the quality of the alternative channels would be hard to estimate.

And when the restriction will likely cover only a particular message — pro-boycott speech, anti-draft speech, and so on — the normal risk of judicial error and deliberate or subconscious prejudice is magnified because the judges know well which side of the political debate will lose as a result of their decision. In such a scenario, it's especially likely that judges will apply the vague "ample alternative channels" standard in a way that's not protective enough of unpopular speakers. It is probably no accident that the low water mark of the requirement, City of Renton v. Playtime Theatres, Inc., involved a restriction that was limited to sexually-themed speech, even though the Court treated the restriction as content-neutral.

Moreover, one restriction aimed at the communicative impact of certain speech is likely to be followed by other such restrictions. Content-based restrictions don't appear randomly: They arise because some fairly powerful segment of society (in government or out of it) believes that a certain kind of speech is dangerous, or — as to laws that aren't facially content-based but are content-based as applied — believes that all conduct that's likely to cause certain effects is dangerous.

If such a group succeeds in restricting, say, Communist speech in some contexts, it seems likely that it will also want to restrict Communist speech in other contexts. Likewise, if a movement tries to restrict bigoted speech in workplaces, perhaps using generally applicable hostile work environment harassment law, it will also likely try to use similar educational and public accommodations harassment rules to restrict speech in educational institutions or places of public accommodation. (That has in fact been the pattern of restrictions on Communist advocacy, antiwar speech, sexually themed speech, pro-civil-rights speech, and racist speech.)

Each success will help validate the pro-restriction forces' positions in the eyes of voters and legislators who are on the fence. Moreover, each success may reinforce the enthusiasm of the supporters of the restrictions. And government restrictions on such speech are also likely to be accompanied by private restrictions on such speech, for instance by private broadcasters, publishers, employers, and commercial property owners. As a result, even when each restriction standing alone imposes only a modest burden on speech, the aggregate of all the restrictions can end up being quite burdensome.

It is, of course, possible for courts to consider this risk, to allow only the first few restrictions, and then to strike down any new restrictions once the alternative channels no longer seem to be ample. But that's a hard project for courts to engage in, especially when they are armed only with the vague "ample alternative channels" standard. Judges may find it hard to explain why they are treating two seemingly similar restrictions differently, simply because of the order in which the restrictions were enacted. And because "ample" lacks an objective absolute definition, courts may end up applying a relative criterion — how many channels the restriction leaves open compared to those available before this restriction was enacted, or how many it leaves open compared to those that it shuts down. If that is so, courts might indeed allow a sequence of restrictions that gradually but substantially reduces the alternative channels, even if the courts would have struck down a restriction that tried to impose the same burden all at once.

Conclusion: For all these reasons, the Court has been right to treat restrictions that are content-based as applied — even if they are facially generally applicable to both speech and conduct — with the same skepticism as it has used for restrictions that are content-based on their face. It's the only approach that is consistent with Hustler, Claiborne Hardware, and the other similar cases. It's properly hostile to the government's attempts to restrict speech because of the informative or persuasive power of the speech. And it's necessary to prevent the government from having the power to broadly suppress certain facts and ideas.

When speech is punished precisely because of what it communicates — for instance, because it may persuade people to violate the law or to boycott someone, because it may offend some listeners, or because it may convey information that helps people commit crimes — the law is operating as a content-based speech restriction. The law is restricting speech precisely because of what is spoken. Therefore, courts should subject such a law to serious First Amendment analysis; they ought not dodge this analysis by simply relabeling the speech as "conduct."