Any cases where the First Amendment was used as an excuse?

Anybody have any links for a case where someone represented clear and present danger and got arrested. And when he was tried he said it was under his first amendment so he was able to say what he said, but he still lost the case. For example, Someone yells ';bomb'; at an airport and gets arrested. I want reliable links please because this is a college paper.Any cases where the First Amendment was used as an excuse?
A recent case you could look up is ';bong hits 4 Jesus.'; It started when the Olympic torch went past a school in Alaska. A student had a banner that said that, and the school suspended him. He appealed his suspension on the grounds that his first amendment right to free speech had been violated. It went all the way to the Supreme Court where he lost. He was off of school grounds at the time, but the court ruled in favor of the district that suspended him because it said that the pro-drug message was inappropriate and that the school could take disciplinary action regardless.