InThe New York Times on March 22, 2012 there was an article titled "Court Appears to Be Wary Hearing Free-Speech Case".  Steven Howards, was arrested by Secret Service agents after approaching Vice-President Cheney and making critical remarks about the Bush administration's war policies.  Mr. Howard also touched the vice-president.  The Supreme court agreed that the secret service agents need to have some lattitude when protecting their charge, especially when placing their own lives in danger.  The issue before the court was whether or not secret service agents who are prepared to take a bullet for the vice president must also be prepared to a retaliatory arrest lawsuit, even when they have probable cause to make an arrest.  Mr. Howard sued the agents saying they violated his First Amendment right to Freedom of Speech!  It's an article worth reading.  Pesonally, if they feel threatened and justified in arresting someone....I would go with their instincts any day!