In constitutional law, a restriction on the exercise of free speech based upon the subject matter or type of speech. Such a restraint is permissible only if it is based on a compelling state interest and is so narrowly worded that it achieves only that purpose. For example, a statute cannot ban all public demonstrations, peaceful or otherwise, on the subject of gun control while allowing demonstrations concerning other topics of controversy. However, a statute can ban all inflammatory speeches, regardless of the topic, that might incite imminent violence. Also called content discrimination. See also discrimination.