In the wake of the 9/11 attacks on the united states, imagine that an Al Qaeda sympathizer stands before a crowd and urges jihad against the United States. He denounces westerners, zionists, and Americans as devils reviled by God. He calls for suicide bombings and other terrorist attacks against infidels, throughout the world but especially in the United States. He urges all lovers of God to try to devise, and if possible to execute, plans of attack against nuclear power plants, water supplies, bridges, and synagogues.

If this imagined Al Qaeda sympathizer did his speech-making elsewhere in the world, the United States would likely convey a protest to the appropriate government and demand that it stop such preaching of hate and violence. Speech, we know, often triggers action. We would dislike having a foreign government sit by until an attack actually occurred. But if the speaker were an American citizen, living in the United States, our government would need to adopt a different posture. The imagined speech would be protected by the First Amendment to the Constitution, as interpreted by the Supreme Court of the United States – at least unless and until the Court could be persuaded to change its mind.