Freedom of expression refers directly to the combination of freedom of speech, freedom of assembly, and freedom of press without government interference. These freedoms are guaranteed to all Americans by the first amendment to the Constitution of the United States.
Essentially, freedom of expression boils down to the right to have our say on any issue, as well as the right to hear what others have to say. For the most part, due to these provisions in the Bill of Rights, all Americans have the right to criticize public officials and their actions without fear of imprisonment or reprisal by any branch of the government.
These freedoms stretch to many forms of expression beyond mere words or writing. Gestures, movements, articles of clothing, and other forms of expressive conduct are considered symbolic speech and are granted substantial protection by the court system. A strong example of this protection is in the Supreme Court case Texas v. Johnson, where burning the American flag was considered to legally be a form of symbolic expression and thus protected by the First Amendment. Even further, in 1992, the Court in R.A.V. v. City of St. Paul, Minnesota, the court stated that the burning of religious symbols or other bias-related disorderly conduct is constitutionally protected provided the actions didn't violate other safety laws.
Prior restraint is also an issue in terms of freedom of expression; can the government restrict something from being stated before it has the opportunity to be stated? In other words, if you have some prior knowledge, can the government prevent you from saying it? The answer, legally, is that with freedom of expression, the government cannot restrict individuals from speaking their mind prior to their action. This was defended in the Pentagon Papers case, New York Times v. United States, in which the Washington Post and the New York Times were about to print some documents obtained illegally pertaining to military action in Vietnam. The Supreme Court said that they could in fact print these papers and that the government could not restrain them.
Another issue in terms of freedom of expression is obscenity. Generally, the court system tries to stay away from this issue by leaving it up to communities themselves to determine what is obscene, but it will largely defend the freedom of expression in any legal situation it has to deal with. A notable exception to this is the possession of child pornography, which is generally outlawed because of its exploitation of children.
Although freedom of expression is very broad and largely protected by the court system in the United States, there are still many elements of expression that are forbidden for various reasons.
Libel and slander, or the statement or publication of false and defamating statements about an individual or group are outlawed. This is illegal because libel and slander can be used to violate the rights of others without merit.
Fighting words are also outlawed, meaning that one cannot use their freedom of speech or press in order to instigate a crowd to acts of violence. This means that it is illegal to utter racial slurs and other such statements in order to instigate violence. Also illegal is heckling, at least to the point where it interferes with the speaker and his or her ability to speak.
Freedom of press and speech are also not allowed in situations of clear and present danger, which means that any speech that causes an immediate or imminent danger to the nation that Congress otherwise could prevent. This includes speaking in such a fashion as to instigate a military conflict with another nation or to incite widespread rioting.
The bad-tendency rule is somewhat more controversial, in that it curtails First Amendment freedoms in the situation that it may directly lead to significant crimes. This rule applies when, for example, an individual repeatedly speaks on behalf of a plot to violently overthrow governments with extreme bloodshed, as was the case in Gitlow v. New York.
In the United States, freedom of expression is a fundamental and well-protected right of all citizens. | 
