Consider the question. Texas v. Johnson, 491 U.S. 397 (1989), was a decision by the Supreme Court of the United States that invalidated prohibitions on desecrating the American flag enforced in 48 of the 50 states. Justice William Brennan wrote for a five-justice majority in holding that the defendant Gregory Lee Johnson's act of flag burning was protected speech under the First Amendment to the United States Constitution. Johnson was represented by attorneys David D. Cole and William Kunstler.

Answer this question based on the passage: how did the supreme court rule in texas v johnson?
What is the step-by-step reasoning process to arrive at the answer: the defendant Gregory Lee Johnson 's act of flag burning was protected speech under the First Amendment to the United States Constitution?
To answer the above question, the relevant sentence is: Justice William Brennan wrote for a five-justice majority in holding that the defendant Gregory Lee Johnson's act of flag burning was protected speech under the First Amendment to the United States Constitution.