In Texas v. Johnson, a divided Supreme Court held that burning the flag was protected expression under the First Amendment. (1989)
part of the majority opinion:
....nothing in our precedents suggests that a State may foster its own view of the flag by prohibiting expressive conduct relating to it. To bring its argument outside our precedents, Texas attempts to convince us that even if its interest in preserving the flag’s symbolic role does not allow it to prohibit words or some expressive conduct critical of the flag, it does permit it to forbid the outright destruction of the flag. . . . .
We are tempted to say, in fact, that the flag’s deservedly cherished place in our community will be strengthened, not weakened, by our holding today. Our decision is a reaffirmation of the principles of freedom and inclusiveness that the flag best reflects, and of the conviction that our toleration of criticism such as Johnson’s is a sign and source of our strength. Indeed, one of the proudest images of our flag, the one immortalized in our own national anthem, is of the bombardment it survived at Fort McHenry. It is the Nation’s resilience, not its rigidity, that Texas sees reflected in the flag—and it is that resilience that we reassert today. The way to preserve the flag’s special role is not to punish those who feel differently about these matters. It is to persuade them that they are wrong. “To courageous, self reliant men, with confidence in the power of free and fearless reasoning applied through the processes of popular government, no danger flowing from speech can be deemed clear and present, unless the incidence of the evil apprehended is so imminent that it may befall before there is opportunity for full discussion. If there be time to expose through discussion the falsehood and fallacies, to avert the evil by the processes of education, the remedy to be applied is more speech, not enforced silence.” Whitney v. California, 274 U.S. 357, 377 (1927) (Brandeis, J., concurring). And, precisely because it is our flag that is involved, one’s response to the flag burner may exploit the uniquely persuasive power of the flag itself. We can imagine no more appropriate response to burning a flag than
waving one’s own, no better way to counter a flag burner’s message than by saluting the flag that burns, no surer means of preserving the dignity even of the flag that burned than by—as one witness here did—according its remains a respectful burial. We do not consecrate the flag by punishing its desecration, for in doing so we dilute the freedom that this cherished emblem represents.