Followup

Here is a video relating to Nick's question:

Alyssa mentioned Brandenburg v. Ohio. You may find a case summary and oral argument here. The short form:

The Court's Per Curiam opinion held that the Ohio law violated Brandenburg's right to free speech. The Court used a two-pronged test to evaluate speech acts: (1) speech can be prohibited if it is "directed at inciting or producing imminent lawless action" and (2) it is "likely to incite or produce such action." The criminal syndicalism act made illegal the advocacy and teaching of doctrines while ignoring whether or not that advocacy and teaching would actually incite imminent lawless action. The failure to make this distinction rendered the law overly broad and in violation of the Constitution.