The First Amendment requires that Congress shall make no law “abridging the freedom of speech.” That means Congress generally can’t make speech a crime. Nonetheless, the Supreme Court has found a few rare and specific categories of speech to be outside the protection of the First Amendment, such as true threats, obscenity, incitement of imminent violence, and speech integral to criminal conduct.

But what if Congress passes a law that applies to both protected and unprotected speech? Although some applications of such a law might be permissible, many others would violate the First Amendment. When a defendant is convicted under such a law for speech not protected by the First Amendment, that defendant may nevertheless challenge his conviction on the ground that the law is “facially overbroad” and criminalizes too much protected speech.

A law is facially overbroad when the amount of unprotected speech that it legitimately forbids is eclipsed by the amount of protected speech that it suppresses. In Ashcroft v. Free Speech Coalition (2002), the Supreme Court explained that overbreadth challenges are necessary because severe penalties for violating an unconstitutional law are enough to deter or “chill” citizens from uttering protected speech, even if those citizens might eventually win a challenge to their convictions if they were ever charged. If a court finds that a law is indeed facially overbroad, the court must invalidate the law in its entirety.

Helaman Hansen was convicted for violating a federal criminal law with sweeping breadth. That federal law criminalizes any speech that “encourages or induces an alien to come to, enter, or reside in the United States, knowing or in reckless disregard of the fact that such coming to, entry, or residence is or will be in violation of law.” Hansen challenged the law as facially overbroad and the Ninth Circuit agreed, striking down the law and vacating Hansen’s conviction. Now the Supreme Court has taken the case, and the Cato Institute has filed an amicus brief supporting Hansen’s argument that the law is impermissibly overbroad.

In the brief, we explain how criminalizing mere “encouragement” or “inducement” of immigration violations endangers the First Amendment rights of anyone in the United States who speaks or writes in support of immigration. Many advocates and organizations urge immigrants to stay in this country and wait for political change, regardless of their legal status. Lawyers will advise some immigrants—quite correctly, in many cases—that remaining in the country (even illegally) will grant them certain constitutional or statutory protections that are unavailable outside the United States. Yet the law on its face threatens jail time for giving such truthful advice.

Cato’s brief also rebuts one of the government’s arguments. Hansen was convicted of not only encouraging or inducing a violation of immigration law but also of doing so for financial gain, which carries an added penalty. The government argues that because Hansen was convicted of this “financial gain” sentence enhancement, the Supreme Court should only consider whether the sentence enhancement is facially overbroad.

The government is wrong. As we argue in our amicus brief, the sentence enhancement is irrelevant to the chilling effect of the underlying prohibition on simply encouraging or inducing immigration violations. Hansen could have been convicted under the statute regardless of whether the government proved that Hansen’s actions were done for financial gain. And even if the overbreadth analysis were limited to encouragement motivated by financial gain, the statute would still criminalize too much protected speech, like that of lawyers and doctors. Either way, the Court should strike down the law as facially overbroad under the First Amendment.