Which is an example of a time when it is legal to restrict citizen's speech?

An example of a time when citizen's right to free speech can be restricted is when their speech impedes national security. For example, Freedom of Speech was greatly restricted during wars (such as WWII), when national security depended on people keeping quiet to not leak information to foreign spies. This was expanded on by the usage of propoganda, and was usually enforced by Civil Officers. Freedom of Speech however generally is not restricted, even when it hurts another group, as seen in National Socialist Party of America v. Village of Skokie, which, while the Justice sympathized with the people of Skokie, it ruled that freedom of speech cannot be denied to even hate groups.

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