Government regulations of speech fall into two categories: content-based restrictions, which prohibit certain types of speech because of what is being said, and content-neutral restrictions, which regulate speech regardless of content and in pursuit of a substantial government purpose. Content-based restrictions usually fail constitutional scrutiny; the government must establish that the law is narrowly tailored to achieve a compelling state interest, and the law must be the least restrictive means for achieving that interest. A total ban on discussion of a certain topic or particular point of view is unlikely to satisfy this strict standard, though certain categories of “non-speech” (speech deemed to be outside of the protection of the First Amendment), including obscenity, child pornography, and fighting words, may be prohibited.
Content-neutral regulations, however, apply to all speech regardless of subject or viewpoint. One category of content-neutral regulations are “time, place, and manner” restrictions on speech, which must still be narrowly drawn and serve a substantial government interest. This category covers, for example, laws that prohibit sidewalk protests during rush hour (where the government interest is preventing potentially dangerous congestion on the sidewalk and in the street), and laws that prohibit sleeping in national parks, even if a group of demonstrators wants to do so as a form of protest.
Time, place, and manner restrictions are typically context-specific and relate to the needs of a particular area, venue, or community. Because of the global nature of the Internet, it would be very difficult to develop or enforce meaningful time, place, and manner restrictions online.