From 1791 to the present … the First Amendment has permitted restrictions upon the content of speech in a few limited areas, and has never included a freedom to disregard these traditional limitations. These historic and traditional categories long familiar to the bar—including obscenity, defamation, fraud, incitement, and speech integral to criminal conduct—are well-defined and narrowly limited classes of speech, the prevention and punishment of which have never been thought to raise any Constitutional problem.
U.S. v. Stevens.
Although the First Amendment stands against any freewheeling authority to declare new categories of speech outside the scope of the First Amendment, the Court has acknowledged that perhaps there exist some categories of speech that have been historically unprotected but have not yet been specifically identified or discussed in our case law. Before exempting a category of speech from the normal prohibition on content-based restrictions, however, the Court must be presented with persuasive evidence that a novel restriction on content is part of a long (if heretofore unrecognized) tradition of proscription.
U.S. v. Alvarez.
So speech outside of the unprotected categories is protected, and courts are not free to invent new categories.
When a statute restricts a real and substantial amount of protected speech, it is void. U.S. v. Stevens doesn’t say this, but that’s what the Court did: “We hold only that §48 is … substantially overbroad, and therefore invalid under the First Amendment.”
Lower courts think that “strict scrutiny” and “overbreadth” are separate analyses. They are probably incorrect.
The analysis applied in Stevens is probably strict scrutiny. This is the first footnote in Brown v. Entertainment Merchants Association:
Justice Alito distinguishes Stevens on several grounds that seem to us ill founded. He suggests that Stevens did not apply strict scrutiny. If that is so (and we doubt it), it would make this an a fortiori case.
Strict scrutiny has two prongs: compelling state interest, and narrow tailoring. To satisfy strict scrutiny the statute must pass both tests.
“Content-based laws—those that target speech based on its communicative content—are presumptively unconstitutional and may be justified only if the government proves that they are narrowly tailored to serve compelling state interests.” That’s R.A.V.
If Stevens applied strict scrutiny, and substantial overbreadth ended the inquiry, then substantial overbreadth is the end of a strict-scrutiny inquiry. If that is so, it is because a statute that is substantially overbroad is by definition not narrowly tailored.
Which makes sense, since too broad is the opposite of narrow enough, and if a restriction fails one prong of strict scrutiny, a court does not have to consider the other. If a statute is not narrowly tailored, a court does not need to consider whether the state had a compelling interest.
Here, have a graphic: